Kjetill Sigurd Jakobsen

• Maurstad, Marius Filomeno; Kusy, Dominik; Undheim, Eivind Andreas Baste; Jakobsen, Kjetill Sigurd; Böhne, Astrid & Monteiro, Rita [Show all 20 contributors for this article] (2026). ERGA-BGE chromosome-level genome assembly of the giant stream lacewing  Osmylus fulvicephalus (Scopoli, 1763). Open Research Europe. 6. doi: 10.12688/openreseurope.23457.3. Full text in Research Archive Show summary

  The giant stream lacewing, Osmylus fulvicephalus (Scopoli, 1763), is a widespread European species belonging to the insect order Neuroptera. Its cryptic larvae are predators found at the banks of streams and smaller rivers where they use their piercing, lance-shaped stylets to inject venom into their arthropod prey. Here, we present the reference genome of the giant stream lacewing as a crucial resource for uncovering the genetic basis of venom evolution in Neuroptera. The chromosome-level genome encompasses 674.7 Mb and is composed of 60 contigs and 24 scaffolds where 99.2% of the assembly is distributed among the 6 contiguous chromosomal pseudomolecules and two sex chromosomes (X and Y). Contig and scaffold N50 have a value of 51.5 Mb and 116.2 Mb, respectively. This reference genome is the first genomic resource from the family of lance lacewings, providing valuable data for clarifying the phylogenetic placement of the family Osmylidae within Neuroptera.

• Strand, Marius André; To, Thu-Hien; Tørresen, Ole Kristian; Fullmer, Sarah; Ferrari, Giada & Skage, Morten [Show all 9 contributors for this article] (2026). The origin of the octoploid cloudberry (Rubus chamaemorus) genome is the result of multiple and complex polyploidization events. Journal of Heredity. ISSN 0022-1503. 117(4), p. 822–833. doi: 10.1093/jhered/esag028. Full text in Research Archive
• Baalsrud, Helle T; Tørresen, Ole K; Danneels, Bram; Ferrari, Giada; Tooming-Klunderud, Ave & Skage, Morten [Show all 12 contributors for this article] (2026). Chromosomal fusions shaped the genome of the greater hornwrack bryozoan (Flustra foliacea) (Linnaeus, 1758). Journal of Heredity. ISSN 0022-1503. 117(4), p. 750–760. doi: https:/academic.oup.com/jhered/article/117/4/750/8497176. Full text in Research Archive Show summary

  The phylum Bryozoa is an understudied, yet commonly occurring, globally distributed bilaterian metazoan organismal group. They have a colonial lifestyle and an evolutionary history that spans at least 480 million years but likely longer. Despite their contentious phylogenetic affinities among metazoans, disproportionately few genomic investigations have been performed thus far. Here, we describe the first chromosome-level genome assembly of an individual Flustra foliacea colony belonging to the order Cheilostomatida, collected in southern Norway. The haplotype-resolved assembly of F. foliacea contains two pseudo-haplotypes spanning 956 megabases and 880 megabases, respectively. Both assemblies are highly complete both in terms of scaffolding (>90% of sequences placed in eight autosomal chromosomal pseudomolecules), and gene content (BUSCO completeness scores >90%). We also present gene and repeat annotations of the two assemblies. A comparison of our newly sequenced F. foliacea with five previously published bryozoan genomes supports the hypothesis that the group has undergone extensive genome rearrangements. This includes multiple chromosomal fusions in F. foliacea since their split with other cheilostome bryozoans. These fusions were enriched with long terminal repeat retrotransposons, highlighting the complex interplay between genome organization and genomic repeats. Our study contributes to a deeper understanding of bryozoan genome evolution and the role of repeats in metazoan genome organization.

• Araya, Robin Aasegg; Maurstad, Marius Filomeno; Wilson, David T; Rash, Lachlan D; Mobli, Mehdi & Jakobsen, Kjetill Sigurd [Show all 7 contributors for this article] (2026). Ancient origin and dynamic evolution of bivalent spider toxins. Molecular Biology and Evolution (MBE). ISSN 0737-4038. 43(5). doi: 10.1093/molbev/msag076. Full text in Research Archive Show summary

  Bivalent peptide toxins comprising 2 cysteine-rich domains have evolved from single-domain precursors on multiple occasions in animal venoms, resulting in enhanced molecular target selectivity and avidity. Although bivalent toxins are emerging as prevalent in animal venoms, the genomic and evolutionary processes driving the transitions between single- and multi-domain architectures remain poorly understood. Here, we investigated the evolution of bivalent inhibitor cystine knot (ICK) toxins in spider venom. We first generated a genome assembly of the tree-dwelling funnel-web spider Hadronyche cerberea, revealing a massive expansion of ICK toxin-encoding genes, including the bivalent π-hexatoxin-Hc1a. All ICK toxin genes share a conserved 3-exon structure, flanked by transposable elements (TEs) that may have facilitated gene expansion. This gene structure is shared by the Hc1a subfamily, where the entire mature bivalent toxin is encoded by the third exon. Leveraging de novo transcriptome assemblies from 86 spider species along with venom proteomic data, we show that bivalency in the Hc1a subfamily is of ancient origin and evolved via intra-exonic duplication not involving introns. This was followed by domain expansion and recurrent domain losses mediated by point mutations, deletions, and unequal crossing-over facilitated by high interdomain sequence similarity. In contrast, the bivalent toxin DkTx from Cyriopagopus schmidti is confined to a small group of tarantulas, where it appears to have evolved once, with subsequent domain losses potentially linked to TE activity. Our findings reveal that singular events of domain duplication can give rise to complex, asymmetrical evolutionary trajectories shaped by gene instability and selective retention of functional domains.

• Solbakken, Monica Hongrø; Tørresen, Ole Kristian; Tooming-Klunderud, Ave; Skage, Morten; Bakken, Torkild & Jakobsen, Kjetill Sigurd (2026). Loss of Major Histocompatibility Complex I and II Function in the Genome of Glacier Lanternfish Provides Insight Into Evolution of Vertebrate Immune Systems. Genome Biology and Evolution (GBE). 18(7). doi: 10.1093/gbe/evag154. Full text in Research Archive
• Cerca, José; Ravinet, Mark; Flagstad, Øystein; Rolandsen, Christer Moe; Strand, Olav & Tørresen, Ole Kristian [Show all 8 contributors for this article] (2026). Hybridization with wild individuals fuels reindeer feralization. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 293(2075), p. 1–11. doi: 10.1098/rspb.2026.1226. Full text in Research Archive Show summary

  Domestication has profoundly influenced the development of human agriculture, and is characterized by intense artificial selection. Feralization occurs when domestic animals return to the wild. Although feralization does not fully reverse domestication traits, the selective pressures and evolutionary mechanisms driving it remain poorly understood. In northern Europe and Asia, wild, semi-domesticated and feral reindeer (Rangifer tarandus) populations coexist, offering a unique opportunity to study feralization. We studied genomic signatures of selection in semi-domesticated, feral and wild reindeer populations in Norway. Analysis of population structure confirmed historical records indicating the feral population formed a monophyletic clade that originated from neighbouring semi-domesticated reindeer. However, we also found evidence for excess allele-sharing between wild and feral reindeer, indicating hybridization between these lineages. Signatures of selection were identified using a top-down approach (orthologues of domestication candidate genes) and a bottom-up approach (FST and extended haplotypes). We found that candidate regions under selection have higher rates of excess allele-sharing between wild and feral populations. This provides the first evidence of reversed selection pressures during feralization in reindeer and reveals a link between selection and hybridization. Together, our findings suggest that hybridization likely promoted adaptive introgression during feralization. We discuss the implications of our findings for conserving the genetic integrity of endangered wild reindeer populations.

• Baalsrud, Helle Tessand; Garmann-Aarhus, Benedicte; Enevoldsen, Emily Louise Gilbert; Krabberød, Anders Kristian; Dominik, Fischer, & Tooming-Klunderud, Ave [Show all 13 contributors for this article] (2026). Centromeric satellite expansion drives genome evolution in the snowy owl. Genome Biology. ISSN 1474-7596. doi: 10.1186/s13059-026-04175-y. Full text in Research Archive Show summary

  Comparative genomic studies in birds have revealed that bird genomes are relatively repeat-poor and stable in terms of karyotype, size, and gene synteny/collinearity compared to other vertebrates. One notable exception is the owls, with cytogenetic studies demonstrating large variations in karyotypes and the evolution of unusual centromeric satellite repeats in some species. However, there has so far not been an investigation into genome architecture and repeat landscape of owls. Here, we present a chromosome-level genome assembly for the snowy owl (Bubo scandiacus). We find that the repeat DNA content in the relatively large snowy owl genome (1.6 Gb) is among the highest reported for any bird genome to date (28.34% compared to an average of ~ 10% in other birds). The bulk of the snowy owl genomic repeat landscape consists of extensive centromeric satellite arrays that form large contiguous blocks across multiple chromosomes. These arrays represent one of the largest centromeric satellite expansions reported in birds and are consistent with rapid turnover and amplification of centromeric repeats. Using gene collinearity analyses we show that the position of the centromeres are not homologous with chicken centromeres, and are located in regions with collinearity breaks to other bird genomes due to chromosomal rearrangements. Our results support rapid satellite turnover at lineage-specific centromeres, which could have played a role in centromeric drive, reproductive isolation and speciation of the snowy owl. The extensive centromeric satellite arrays uncovered in this genome highlight centromere evolution as a potentially important driver of genome evolution in owls.

• Guslund, Naomi Croft; Jonsson, Alexandra; Krabberød, Anders Kristian; Porras, Adrian Lopez; Nørstebø, Simen Foyn & Sørum, Henning [Show all 9 contributors for this article] (2026). IgM-mediated protection drives early B-cell activation and mucosal containment of Vibrio anguillarum in Atlantic cod (Gadus morhua). Frontiers in Immunology. 17. doi: 10.3389/fimmu.2026.1771403. Full text in Research Archive Show summary

  Background: Atlantic cod lack functional MHC class II and CD4, raising fundamental questions about how vaccination generates protection in this species. Methods: We combined single-cell transcriptomic profiling of splenic cells with qRT-PCR across complementary active vaccination and passive serum-transfer experiments to define cellular and transcriptional correlates of immunity to Vibrio anguillarum. Results: Bath-vaccinated fish and recipients of immune serum showed effective containment of infection, with bacterial signals largely restricted to gills and minimal detection in spleen or head kidney, whereas naïve fish frequently developed high systemic bacterial loads by day 3 post-infection. All groups exhibited increased splenic macrophage abundance following challenge, but only naïve fish showed strong and sustained inflammatory activation, consistent with their higher pathogen burden. Vaccinated fish and immune-serum recipients displayed only transient or weak myeloid responses despite similar early neutrophil activation. Across both experimental models, a transcriptionally distinct B-cell subset expanded at the peak of infection. This population showed increased immunoglobulin and MHC class I expression together with innate sensing features, consistent with an activated B-cell state. Although this B-cell subset increased in all groups, the largest expansions were observed in vaccinated fish and immune-serum recipients. Overall, these findings are consistent with antigen-specific IgM enhancing early B-cell activation and contributing to protection against V. anguillarum through coordinated humoral and innate-like B-cell responses. Discussion: These findings identify an antibody-driven mode of immune coordination that operates independently of classical CD4+ T-cell help and provide insight into how effective vaccination can be achieved in vertebrates with divergent adaptive immune architectures.

• Hoff, Siv Nam Khang; Maurstad, Marius Filomeno; Tørresen, Ole K.; Araya, Robin Aasegg; Berg, Paul R. & Præbel, Kim [Show all 8 contributors for this article] (2026). Rapid genome modifications including chromosomal fusions and large-scale inversions are key features in Arctic codfish species. Genome Biology. ISSN 1474-7596. 27. doi: 10.1186/s13059-026-03975-6. Full text in Research Archive Show summary

  Genome evolvability involves activation of transposable elements (TEs) that result in novel genomic rearrangements, including translocations, deletions, duplications, as well as larger structural reorganizations, such as chromosomal inversions and fusions. These genomic modifications contribute to raw genetic variability in which selection can act upon, and thus, promote local adaptation. Results Using a comparative genomics framework combined with the generation of six chromosome-level gadid reference genomes, including the cold-water adapted polar cod ( Boreogadus saida ) and Arctic cod ( Arctogadus glacialis ), we uncover an array of larger and smaller chromosomal reorganizations within this lineage. For the two Arctic codfishes, we detect lineage-specific chromosomal fusions, i.e., five in polar cod vs. eight in Arctic cod, resulting in a reduced number of chromosomes found to be associated with their geographical distribution. For the same species, we identify a high number of partly overlapping chromosomal inversions where a majority (especially within breakpoint regions) display an overrepresentation of specific TE families, accompanied by signatures of high degree of conservation. We further demonstrate involvement of miniature inverted-repeat transposable elements (MITEs) in the expansion of the well-known antifreeze glycoprotein genes in polar cod, and that the three gene clusters were localized in association with chromosomal rearrangements on chromosomes 1, 2, and 14. Conclusions We characterize how the Gadidae lineage has undergone massive genomic modifications — potentially via activation of TEs — throughout their evolutionary history, and particularly for the more Arctic species. These genomic reorganizations have likely played an important role in divergence processes and adaptation to freezing environmental conditions.

• Tørresen, Ole K; Tooming-Klunderud, Ave; Skage, Morten; Streitlien, Anne Eline; Strand, Olav & Rolandsen, Christer Moe [Show all 10 contributors for this article] (2025). Chromosome-level genome assembly of Norwegian wild alpine reindeer (Rangifer tarandus tarandus). Journal of Heredity. ISSN 0022-1503. doi: 10.1093/jhered/esaf094. Full text in Research Archive Show summary

  We describe a chromosome-level genome assembly from a wild alpine reindeer individual (Rangifer tarandus tarandus) from the Rondane area in Southern Norway. The assembly is resolved into two pseudo-haplotypes: hap 1 spanning 3,081 Mb and hap 2 spanning 2,633 Mb. Contig N50 and scaffold N50 lengths are in the range of 31 to 41 and 66 to 69 Mb, respectively. A large part of these two haplotypes (83.8% and 90.4%, respectively) are scaffolded into 34 autosomal chromosomal pseudomolecules, and in sex chromosomes X and Y for hap 1. The BUSCO completeness scores are 98.0% and 95.2%, respectively, and gene annotations of the assemblies identified 37,998 and 36,977 protein-coding genes. We also present an updated and improved genome assembly for Svalbard reindeer (Rangifer tarandus platyrhynchus; contig N50 46 to 48 Mb, scaffold N50 67 to 71 Mb, BUSCO 95.4% to 98.0%) and a comparison with previously published genome assemblies of reindeer.

• Maurstad, Marius Filomeno; Hoff, Siv Nam Khang; Cerca, José; Ravinet, Mark; Bradbury, Ian & Jakobsen, Kjetill Sigurd [Show all 8 contributors for this article] (2025). Reference genome bias in light of species-specific chromosomal reorganization and translocations. Genome Biology. ISSN 1465-6906. 26(1), p. 1–26. doi: 10.1186/s13059-025-03761-w. Full text in Research Archive Show summary

  Abstract Background Whole-genome sequencing efforts, have during the past decade, unveiled the central role of genomic rearrangements—such as chromosomal inversions—in evolutionary processes, including local adaptation in a wide range of taxa. However, employment of reference genomes from distantly or even closely related species for mapping and the subsequent variant calling can lead to errors and/or biases in the datasets generated for downstream analyses. Results Here, we capitalize on the recently generated chromosome-anchored genome assemblies for Arctic cod ( Arctogadus glacialis ), polar cod ( Boreogadus saida ), and Atlantic cod ( Gadus morhua ) to evaluate the extent and consequences of reference bias on population sequencing datasets (approx. 15–20 × coverage) for both Arctic cod and polar cod. Our findings demonstrate that the choice of reference genome impacts the mapping statistics, including mapping depth and mapping quality, as well as core population genetic estimates, such as heterozygosity levels, nucleotide diversity (π), and cross-species genetic divergence (D XY ). Furthermore, using a more distantly related reference genome can lead to inaccurate detection and characterization of chromosomal inversions, i.e., in terms of size (length) and location (position), due to inter-chromosomal reorganizations between species. Additionally, we observe that some of the verified species-specific inversions are split across multiple genomic regions when mapped against a heterospecific reference. Conclusions Inaccurate identification of chromosomal rearrangements as well as biased population genetic measures could potentially lead to erroneous interpretation of species-specific genomic diversity, impede the resolution of local adaptation, and thus, impact predictions of their genomic potential to respond to climatic and other environmental perturbations.

• Araya, Robin Aasegg; Reinar, William Brynildsen; Tørresen, Ole K; Goubert, Clément; Daughton, Tara Jane & Hoff, Siv Nam Khang [Show all 12 contributors for this article] (2025). Chromosomal Inversions Mediated by Tandem Insertions of Transposable Elements. Genome Biology and Evolution (GBE). 17(8). doi: 10.1093/gbe/evaf131. Full text in Research Archive Show summary

  Chromosomal inversions play a crucial role in evolution by influencing phenotypes through the linkage of coadapted alleles. While inversions have been found across a large number of taxa, mapping and characterizing inversion breakpoint regions remain challenging, often due to the presence of complex tandem repeats and transposable elements. Here, we identify and quantify transposable elements in the breakpoints of the four large-scale inversions previously reported in Atlantic cod, leveraging on three high-quality long-read-based reference genome assemblies for the Norwegian Coastal cod, the Northeast Arctic cod, and Celtic cod ecotypes. We detected a significant enrichment of transposable element orders and superfamilies with terminal inverted repeats within the inversion breakpoint regions of chromosomes 1, 7 and 12. Notably, we discovered a tandem accumulation of miniature inverted-repeat transposable elements belonging to a family of hAT transposons, exclusively residing in the breakpoints of the inverted haplotype on chromosomes 1 and 7 found in the Northeast Arctic cod. The accumulation of tandemly arranged transposable elements with high sequence similarity in breakpoint regions suggests that they have driven the appearance of inversions through ectopic recombination, further supporting the potential of transposable elements in facilitating chromosomal reorganizations with large evolutionary implications.

• Blaxter, Mark; Lewin, Harris A.; DiPalma, Federica; Challis, Richard; Silva, Manuela da & Durbin, Richard [Show all 31 contributors for this article] (2025). The Earth BioGenome Project Phase II: illuminating the eukaryotic tree of life. Frontiers in Science. 3. doi: 10.3389/fsci.2025.1514835. Full text in Research Archive Show summary

  The Earth BioGenome Project (EBP) aims to “sequence life for the future of life” by generating high-quality reference genome sequences for all recognized eukaryotic species, thereby building a rich knowledge base to inform conservation, inspire bioindustry, ensure food security, advance medicine, and establish a deeper understanding of biodiversity. As the EBP works toward completing the original Phase I goal—a reference genome for each of the approximately 10,000 taxonomic families of eukaryotes—milestone publications have demonstrated the transformative potential of the project. The EBP has promoted global collaboration and established core methods and standards. By the end of 2024, EBP-affiliated projects had publicly released 2,000 high-quality genome assemblies, representing more than 500 eukaryotic families. In this article, we present a revised set of goals for Phases I and II of the EBP. For Phase II, we propose generating reference genomes for 150,000 species over 4 years, including representative genomes for at least 50% of all accepted genera and for additional species of biological and economic importance. To deliver Phase II, EBP-affiliated projects will have to release over 3,000 new genomes per month. We review the magnitude of the tasks in sourcing, sequencing, assembling, annotating, and analyzing genomes at this scale, and explore the scientific, technical, social, legal, ethical, and funding challenges associated with them. Success in Phase II will set the stage for sequencing the remaining ~1.5 million named species of Eukaryota and establishing the knowledge platforms necessary for understanding, preserving, and utilizing Earth’s biodiversity in an era of rapid environmental change.

• Tellini, Nicolo; Tørresen, Ole K.; Edwards, David; Rieseberg, Loren H.; Jakobsen, Kjetill Sigurd & Cerca, José (2025). Pangenomes as a framework for adaptive radiation, speciation, and adaptation. American Journal of Botany. ISSN 0002-9122. 112(12), p. 1–4. doi: 10.1002/ajb2.70130. Full text in Research Archive Show summary

  Understanding the genomic basis of diversification is a central goal in evolutionary biology. In recent years, the development and use of pangenomes, a genomic representation of multiple individuals within a lineage (a set of related populations, subspecies, ecotypes, or species), has enabled researchers to differentiate between DNA sequences shared by all individuals of a given lineage (core regions) from those present only in some individuals (accessory or variable regions). Differentiating between core and accessory regions has highlighted a key limitation of relying on a single reference genome: It captures the genetic code of only one individual and this biases genomic analyses and our understanding of diversification. Here, we propose that by identifying genes associated with both core and accessory regions, we can deepen our understanding of the processes underlying diversification. We suggest that analyzing pangenomes and accessory regions will provide deeper insights into diversification, hybridization, and the genetic basis of adaptation and speciation.

• Maurstad, Marius Filomeno; Ramiro, Iris Bea; Øyen, Jan Philip; Sombke, Andy; Büsse, Sebastian & Nachtigall, Pedro Gabriel [Show all 8 contributors for this article] (2025). The green lacewing venom system and the complex mechanisms underlying its evolution. Molecular Biology and Evolution (MBE). ISSN 0737-4038. 43. doi: 10.1093/molbev/msaf326. Full text in Research Archive Show summary

  Abstract Venom has independently evolved across many lineages, yet relatively few have been studied in detail, particularly among insects. Of these, Neuroptera (lacewings, antlions and relatives) remain largely unexplored, despite being widespread with agriculturally important groups such as green lacewings. While adults are non-venomous, neuropteran larvae are ferocious predators that use pincer-like mouthparts to inject paralysing and liquefying venom to subdue and consume their prey. Here, we provide a comprehensive investigation of the venom system in Neuroptera by integrating a high-quality genome, long-read transcriptomes spanning all life stages, microCT-reconstruction of venom glands, tissue-specific expression analyses, venom proteomics, and functional assays of the common green lacewing Chrysoperla carnea. We provide a re-description of the neuropteran venom system, demonstrate the venom’s insecticidal and cytotoxic activity, and show the venom comprises diverse toxin gene families and is richer and more similar to the venom of antlions than previously proposed. We show that this toxin arsenal is the result of a multitude of evolutionary events that include co-option, recruitment following gene duplication, diversification of toxin-paralogs by gene duplication, and functional innovation of new paralogs through both small structural and large architectural changes. In addition, we find that alternative splicing of toxin genes is an important contributor to the biochemical arsenal, which is a mechanism rarely documented among venomous animals. Our results demonstrate how multiple genomic and evolutionary mechanisms together contribute to the emergence and evolution of a complex molecular trait, and provide new insights into the evolution of venom in insects.

• Kersten, Oliver Sven; Star, Bastiaan; Anker-Nilssen, Tycho; Strøm, Hallvard; Jakobsen, Kjetill Sigurd & Boessenkool, Sanne (2025). Single Nucleotide Polymorphisms, Structural Variants, and Short Tandem Repeats Capture Distinct Signals of Adaptive Divergence in the Atlantic Puffin. Genome Biology and Evolution (GBE). 17(9), p. 1–17. doi: 10.1093/gbe/evaf162. Full text in Research Archive Show summary

  The Arctic has been the scene for (re)colonization, diversification, and adaptation of boreal and Arctic fauna. As anthropogenic warming of the Arctic environment increases the extinction risk for peripheral populations, understanding patterns of local adaptation is imperative. The Atlantic puffin (Fratercula arctica) comprises multiple genetically and morphologically distinct populations with an Arctic-boreal distribution. Yet, patterns of adaptation between these populations remain poorly understood. Here, we investigate potential adaptive divergence between High Arctic (F. a. naumanni) and boreal (F. a. arctica) puffin subspecies using whole-genome sequence data. We analyze different types of intraspecific DNA variation, including single nucleotide polymorphisms (SNPs), structural variants (SVs) and short tandem repeats (STRs). Patterns of elevated levels of genetic divergence vary across these types, with STRs uncovering the largest unique proportion (47.2%) of genomic outlier loci. Notably, 94.5% of all outlier genes are exclusive to one type of variation and several such genes are linked to phenotypic differences observed between these subspecies, including body size, skeletal development, adipose tissue accumulation and the sensory system. Our observations indicate that F. a. naumanni harbors unique genetic diversity within puffins suggesting adaptation to its Arctic environment. Importantly, we show that SNPs, SVs, and STRs capture distinct signals of adaptive divergence, underscoring the importance of integrating multiple genomic markers to fully understand the complexity of local adaptation. These results offer a broader perspective on genomic patterns of adaptive divergence in Arctic fauna and can inform conservation strategies aimed at preserving genetic diversity in the Atlantic puffin.

• Helmerson, Cecilia; Durant, Joël; Hoff, Siv Nam Khang; Brieuc, Marine Servane Ono; Berg, Paul Ragnar & Jorde, Per Erik [Show all 14 contributors for this article] (2025). A century of anthropogenic perturbations impact genomic signatures of the iconic migratory Atlantic cod. Science Advances. 11(31). doi: 10.1126/sciadv.adp3342. Full text in Research Archive Show summary

  Anthropogenic stressors have led to marked ecosystem perturbations, including population declines and shifts in habitat range for key marine fish species. Understanding how these changes affect genome-wide characteristics, causing long-term evolutionary responses, is still in its infancy. Genome-wide retrospective assessment of the iconic migratory Atlantic cod ( Gadus morhua ) from the Barents Sea, unraveled varying degree of admixture with the nonmigratory coastal ecotype throughout the 20th century, and intriguingly more intensified during recent decades. These genomic changes were supported by an increased number of individuals displaying the heterozygous state of the chromosomal inversion coupled to migratory behavior in Atlantic cod. Ecological models and genome-wide scans identified that some of the observed frequency shifts, coupled to neural development, metabolic, and growth regulation, covaried with intensified fisheries, reduced generation time, and ocean warming. Our results demonstrate how anthropogenic perturbations impact the dynamics between two well-known ecotypes of Atlantic cod and thus, their genomic signatures, with potential implications for future management programs.

• Solbakken, Monica Hongrø; Tørresen, Ole K.; Tooming-Klunderud, Ave; Skage, Morten; Bakken, Torkild & Jakobsen, Kjetill Sigurd (2025). The genome of the Glacier lanternfish shows loss of MHC I and II function and provides insight into evolution of lanternfish immune systems. bioRxiv - the preprint server for biology. doi: https:/www.biorxiv.org/content/10.1101/2025.08.28.672920v1. Full text in Research Archive Show summary

  Lanternfishes (Myctophidae) are one of the most abundant and species diverse orders inhabiting the mesopelagic zone. Exploitation of marine resources has recently attracted increased interest. It is therefore essential to improve our understanding of the meso- and deep pelagic ecosystems with respect to conservation and management strategies. Genomic resources are paramount to enable in-depth studies of population structuring and understanding the inherent genetic diversity, but also to enable studies of processes such as local adaptation and selection. Here we present a genome assembly of the Glacier lanternfish (Benthosema glaciale) generated with long-read PacBio and Hi-C contact map data. By comparing additional available genomes from the Myctophiformes order we explore their adaptive immune strategies. Our findings reveal that multiple lineages within this order have lost a significant proportion of genes related to adaptive immunity (Electrona, Protomyctophum and Benthosema). We find simultaneous loss of both classical MHC class I and class II function coinciding with reduction in genetic diversity with respect to immunoglobulin and T-cell receptors. In contrast, the sister branch represented by Gymnoscopelus and Nannobrachium appear to have maintained the standard configuration of the jawed vertebrate adaptive immune system apart from large gene expansions in MHC class II. Our results demonstrate that the Benthosema-belonging lineage (Myctophinae) has completely lost the core functions of the adaptive immune system. How, when and why this occurred warrants further investigations.

• Martin, Sarah Louise; Torre, Renato La; Danneels, Bram; Tooming-Klunderud, Ave; Skage, Morten & Kollias, Spyridon [Show all 12 contributors for this article] (2025). Haplotype-resolved chromosome-level genome assemblies of four Diamesa species reveal the genetic basis of cold tolerance and high-altitude adaptations in arctic chironomids. GigaScience. doi: 10.1093/gigascience/giaf160. Full text in Research Archive Show summary

  Background Arctic and alpine insects experience extreme environmental stressors, yet the genomic basis of their adaptation is poorly understood. Diamesa midges (Diptera: Chironomidae) are cold-adapted insects inhabiting glacial and high-altitude freshwater ecosystems, but no chromosome-level genomes have been available to date. Findings We present the first haplotype-resolved, chromosome-level genomes for four Diamesa species (D. hyperborea, D. lindrothi, D. serratosioi and D. tonsa), assembled using PacBio HiFi sequencing and Hi-C scaffolding. The assemblies show high completeness and k-mer representation. Phylogenomic analyses place Diamesinae as sister to other Chironomidae except Podonominae, and comparisons suggest introgression between the distinct species D. hyperborea and D. tonsa. Comparative genomic analyses across 20 Diptera species identified significant gene family contractions in Diamesa related to oxygen transport and metabolism, consistent with adaptation to high-altitude, low-oxygen environments. Expansions were observed in histone-related and Toll-like receptor gene families, suggesting roles in chromatin remodeling and immune regulation under cold stress. A glucose dehydrogenase gene family was significantly expanded across all cold-adapted species studied, implicating it in cryoprotectant synthesis and oxidative stress mitigation. Diamesa exhibited the largest gene family contraction at any phylogenetic node, with limited overlap in expansions with other cold-adapted Diptera, indicating lineage-specific adaptation. Conclusions Our findings support the hypothesis that genome size condensation and selective gene family changes underpin survival in cold environments. These new genome assemblies provide a valuable resource for studying adaptation, speciation, and conservation in cold-specialist insects. Future integration of gene expression and population genomics will further clarify the evolutionary resilience of Diamesa in a warming world.

• Tørresen, Ole Kristian; Garmann-Aarhus, Benedicte; Hoff, Siv Nam Khang; Jentoft, Sissel; Svensson, Mikael & Schartum, Eivind Sandvik [Show all 11 contributors for this article] (2025). Comparison of whole-genome assemblies of European river lamprey (Lampetra fluviatilis) and brook lamprey (Lampetra planeri). Journal of Heredity. ISSN 0022-1503. 117, p. 96–106. doi: 10.1093/jhered/esaf036. Full text in Research Archive
• Strand, Marius André; To, Thu-Hien; Tørresen, Ole Kristian; Fullmer, Sarah; Skage, Morten & Tooming-Klunderud, Ave [Show all 8 contributors for this article] (2025). Chromosome-level assembly of the octoploid cloudberry (Rubus chamaemorus). BioRxiv. ISSN 0362-4331. doi: 10.1101/2025.07.07.663483. Full text in Research Archive
• Baalsrud, Helle Tessand; Garmann-Aarhus, Benedicte; Enevoldsen, Emily Louise Gilbert; Krabberød, Anders Kristian; Fischer, Dominik & Tooming-Klunderud, Ave [Show all 13 contributors for this article] (2024). Evolutionary new centromeres in the snowy owl genome putatively seeded from a transposable element. BioRxiv. ISSN 0362-4331. doi: 10.1101/2024.07.05.602039. Full text in Research Archive
• Bjørnestad, Synne Arstad; Solbakken, Monica Hongrø; Krokene, Pia; Thiede, Bernd; Hylland, Ketil & Jakobsen, Kjetill Sigurd [Show all 9 contributors for this article] (2024). The Atlantic Cod MHC I compartment has the properties needed for cross-presentation in the absence of MHC II. Scientific Reports. 14(1). doi: 10.1038/s41598-024-76225-z. Full text in Research Archive Show summary

  Atlantic cod has a peculiar immune system, characterized by the loss of Major Histocompatibility Complex (MHC) class II pathway, and an extreme expansion of the MHC class I gene repertoire. This has led to the hypothesis that some of the MHC I variants have replaced MHC II by presenting exogenous-peptides in a process similar to cross-presentation. In mammals, MHC I loads endogenous antigens in the endoplasmic reticulum, but we recently found that different Atlantic cod MHC I gene variants traffic to endolysosomes. There, they colocalize with Tapasin and other components of the peptide-loading complex, indicating a plausible peptide-loading system outside the endoplasmic reticulum. In this study, we further characterize the identity of the Atlantic cod MHC I compartment (cMIC). We found that, similarly to mammalian MHC II compartment, cMIC contains late endosomal markers such as Rab7, LAMP1 and CD63. Furthermore, we identified Hsp90b1 (also known as grp94) and LRP1 (also known as CD91) as interactors of MHC I by mass spectrometry. As these two proteins are involved in cross-presentation in mammals, this further suggests that Atlantic cod MHC I might use a similar mechanism to present exogenous peptides, thus, compensating for the absence of MHC II.

• Tørresen, Ole K.; Kersten, Oliver Sven; Garmann-Aarhus, Benedicte; Helberg, Morten; Tooming-Klunderud, Ave & Skage, Morten [Show all 8 contributors for this article] (2024). A chromosome-level genome assembly of the common eider, Somateria mollissima (Linnaeus, 1758). Journal of Heredity. ISSN 0022-1503. doi: 10.1093/jhered/esae042. Full text in Research Archive Show summary

  The common eider, Somateria mollissima mollissima (Chordata; Aves; Anseriformes; Anatidae), is a large sea duck with a circumpolar distribution. We here describe a chromosome-level genome assembly from an individual female. The haplotype-resolved assembly contains one pseudo-haplotype spanning 1,205 megabases (with both Z and W sex chromosomes) and one pseudo-haplotype spanning 1,080 megabases. Most of these two assemblies (91.13% and 93.18%, respectively) are scaffolded into 32 autosomal chromosomal pseudomolecules plus Z and W for pseudo-haplotype one. The BUSCO completeness scores are 94.0% and 89.9%, respectively, and gene annotations of the assemblies identified 17,479 and 16,315 protein coding genes. Annotation of repetitive sequences classify 17.84% and 14.62% of pseudo-haplotype one and two, respectively, as repeats. The genome of the common eider will be a useful resource for the widely distributed northern species in light of climate change and anthropogenic threats.

• Jentoft, Sissel; Tørresen, Ole K.; Tooming-Klunderud, Ave; Skage, Morten; Kollias, Spyridon & Jakobsen, Kjetill Sigurd (2024). The genome sequence of the Atlantic cod, Gadus morhua (Linnaeus, 1758). Wellcome Open Research. 9. doi: 10.12688/wellcomeopenres.21122.1. Full text in Research Archive Show summary

  We present a genome assembly from an individual male Gadus morhua (the Atlantic cod; Chordata; Actinopteri; Gadiformes; Gadidae). The genome sequence is 669.9 megabases in span. Most of the assembly is scaffolded into 23 chromosomal pseudomolecules. Gene annotation of this assembly on Ensembl identified 23,515 protein coding genes.

• Reinar, William Brynildsen; Krabberød, Anders Kristian; Lalun, Vilde Olsson; Butenko, Melinka Alonso & Jakobsen, Kjetill Sigurd (2024). Short tandem repeats delineate gene bodies across eukaryotes. Nature Communications. 15(1), p. 1–13. doi: 10.1038/s41467-024-55276-w. Full text in Research Archive Show summary

  Short tandem repeats (STRs) have emerged as important and hypermutable sites where genetic variation correlates with gene expression in plant and animal systems. Recently, it has been shown that a broad range of transcription factors (TFs) are affected by STRs near or in the DNA target binding site. Despite this, the distribution of STR motif repetitiveness in eukaryote genomes is still largely unknown. Here, we identify monomer and dimer STR motif repetitiveness in 5.1 billion 10-bp windows upstream of translation starts and downstream of translation stops in 25 million genes spanning 1270 species across the eukaryotic Tree of Life. We report that all surveyed genomes have gene-proximal shifts in motif repetitiveness. Within genomes, variation in gene-proximal repetitiveness landscapes correlated to the function of genes; genes with housekeeping functions were depleted in upstream and downstream repetitiveness. Furthermore, the repetitiveness landscapes correlated with TF binding sites, indicating that gene function has evolved in conjunction with cis-regulatory STRs and TFs that recognize repetitive sites. These results suggest that the hypermutability inherent to STRs is canalized along the genome sequence and contributes to regulatory and eco-evolutionary dynamics in all eukaryotes.

• Dussex, Nicolas; Tørresen, Ole Kristian; Valk, Tom van der; Moullec, Mathilde Le; Veiberg, Vebjørn & Tooming-Klunderud, Ave [Show all 17 contributors for this article] (2023). Adaptation to the High-Arctic island environment despite long-term reduced genetic variation in Svalbard reindeer. iScience. 26(10). doi: 10.1016/j.isci.2023.107811. Full text in Research Archive Show summary

  Typically much smaller in number than their mainland counterparts, island populations are ideal systems to investigate genetic threats to small populations. The Svalbard reindeer (Rangifer tarandus platyrhynchus) is an endemic subspecies that colonized the Svalbard archipelago ca. 6,000–8,000 years ago and now shows numerous physiological and morphological adaptations to its arctic habitat. Here, we report a de-novo chromosome-level assembly for Svalbard reindeer and analyze 133 reindeer genomes spanning Svalbard and most of the species’ Holarctic range, to examine the genomic consequences of long-term isolation and small population size in this insular subspecies. Empirical data, demographic reconstructions, and forward simulations show that long-term isolation and high inbreeding levels may have facilitated the reduction of highly deleterious—and to a lesser extent, moderately deleterious—variation. Our study indicates that long-term reduced genetic diversity did not preclude local adaptation to the High Arctic, suggesting that even severely bottlenecked populations can retain evolutionary potential.

• Konstantinidis, Ioannis; Sætrom, Pål; Brieuc, Marine Servane Ono; Jakobsen, Kjetill Sigurd; Liedtke, Hannes & Pohlmann, Caroline [Show all 8 contributors for this article] (2023). DNA hydroxymethylation differences underlie phenotypic divergence of somatic growth in Nile tilapia reared in common garden. Epigenetics. ISSN 1559-2294. 18(1). doi: 10.1080/15592294.2023.2282323. Full text in Research Archive Show summary

  Phenotypic plasticity of metabolism and growth are essential for adaptation to new environmental conditions, such as those experienced during domestication. Epigenetic regulation plays a key role in this process but the underlying mechanisms are poorly understood, especially in the case of hydroxymethylation. Using reduced representation 5-hydroxymethylcytosine profiling, we compared the liver hydroxymethylomes in full-sib Nile tilapia with distinct growth rates (3.8-fold difference) and demonstrated that DNA hydroxymethylation is strongly associated with phenotypic divergence of somatic growth during the early stages of domestication. The 2677 differentially hydroxymethylated cytosines between fast- and slow-growing fish were enriched within gene bodies (79%), indicating a pertinent role in transcriptional regulation. Moreover, they were found in genes involved in biological processes related to skeletal system and muscle structure development, and there was a positive association between somatic growth and 5hmC levels in genes coding for growth factors, kinases and receptors linked to myogenesis. Single nucleotide polymorphism analysis revealed no genetic differentiation between fast- and slow-growing fish. In addition to unveiling a new link between DNA hydroxymethylation and epigenetic regulation of growth in fish during the initial stages of domestication, this study indicates that epimarkers may be applied in selective breeding programmes for superior phenotypes.

• Kersten, Oliver Sven; Star, Bastiaan; Krabberød, Anders Kristian; Atmore, Lane; Tørresen, Ole K. & Anker-Nilssen, Tycho [Show all 12 contributors for this article] (2023). Hybridization of Atlantic puffins in the Arctic coincides with 20th-century climate change. Science Advances. 9(40). doi: 10.1126/sciadv.adh1407. Full text in Research Archive Show summary

  The Arctic is experiencing the fastest rates of global warming,leading to shifts in the distribution of its biota and increasing the potential for hybridization. However, genomic evidenc eof recent hybridization events in the Arctic remains unexpectedly rare. Here, we use whole-genome sequencing of contemporary and 122-year-old historical specimens to investigate the origin of an Arctic hybrid population of Atlantic puffins(Fratercula arctica) on Bjørnøya, Norway. We show that the hybridization between the High Arctic, large-bodied subspecies F.a. naumanni and the temperate, smaller-sized subspecies F.a. arctica began as recently as six generations ago due to an unexpected southward range expansion of F.a. naumanni. Moreover, we find a significant temporal loss of genetic diversity across Arctic and temperate puffin populations.Our observations provide compelling genomic evidence of the impacts of recent distributional shifts and loss of diversity in Arctic communities during the 20th century.

• Bjørnestad, Synne Arstad; Solbakken, Monica Hongrø; Jakobsen, Kjetill Sigurd; Jentoft, Sissel; Bakke, Oddmund & Progida, Cinzia (2023). Atlantic cod (Gadus morhua) MHC I localizes to endolysosomal compartments independently of cytosolic sorting signals. Frontiers in Cell and Developmental Biology. 11, p. 1–15. doi: 10.3389/fcell.2023.1050323. Full text in Research Archive Show summary

  Major histocompatibility complex (MHC) class I and II are crucial for the adaptive immune system because they are involved in peptide presentation to T cells. Until recently, it was believed that MHC genes and their associated immune components had been conserved since their evolutionary emergence in jawed fish. However, sequencing of the Atlantic cod ( Gadus morhua ) genome revealed a loss of MHC class II genes, and an extreme expansion of MHC class I genes. These findings lead to the hypothesis that a loss of the MHC class II pathway coincided with a more versatile use of MHC class I, but so far there is no direct experimental evidence in support of this. To gain a deeper understanding of the function of the expanded MHC class I, we selected five MHC class I gene variants representing five of the six clades identified in previous studies and investigated their intracellular localization in human and Atlantic cod larval cells. Intriguingly, we uncovered that all selected MHC class I variants localize to endolysosomal compartments in Atlantic cod cells. Additionally, by introducing point mutations or deletions in the cytosolic tail, we found that hypothetical sorting signals in the MHC class I cytosolic tail do not influence MHC class I trafficking. Moreover, we demonstrated that in Atlantic cod, tapasin and MHC class I colocalize on endolysosomes suggesting that peptide-loading assistance and stabilization of MHC class I occurs outside the endoplasmic reticulum. Altogether, our results demonstrate that MHC class I from Atlantic cod is sorted to the endolysosomal system, which may indicate that it interacts with exogenous peptides for potential cross presentation.

• Theissinger, Kathrin; Fernandes, Carlos; Formenti, Giulio; Bista, Iliana; Berg, Paul Ragnar & Bleidorn, Christoph [Show all 55 contributors for this article] (2023). How genomics can help biodiversity conservation. Trends in Genetics. ISSN 0168-9525. 39(7), p. 545–559. doi: 10.1016/j.tig.2023.01.005. Full text in Research Archive Show summary

  The availability of public genomic resources can greatly assist biodiversity assessment, conservation, and restoration efforts by providing evidence for scientifically informed management decisions. Here we survey the main approaches and applications in biodiversity and conservation genomics, considering practical factors, such as cost, time, prerequisite skills, and current shortcomings of applications. Most approaches perform best in combination with reference genomes from the target species or closely related species. We review case studies to illustrate how reference genomes can facilitate biodiversity research and conservation across the tree of life. We conclude that the time is ripe to view reference genomes as fundamental resources and to integrate their use as a best practice in conservation genomics.

• Reinar, William Brynildsen; Tørresen, Ole K.; Nederbragt, Lex; Matschiner, Michael; Jentoft, Sissel & Jakobsen, Kjetill Sigurd (2023). Teleost genomic repeat landscapes in light of diversification rates and ecology. Mobile DNA. 14(1), p. 1–12. doi: 10.1186/s13100-023-00302-9. Full text in Research Archive Show summary

  Repetitive DNA make up a considerable fraction of most eukaryotic genomes. In fish, transposable element (TE) activity has coincided with rapid species diversification. Here, we annotated the repetitive content in 100 genome assemblies, covering the major branches of the diverse lineage of teleost fish. We investigated if TE content correlates with family level net diversification rates and found support for a weak negative correlation. Further, we demonstrated that TE proportion correlates with genome size, but not to the proportion of short tandem repeats (STRs), which implies independent evolutionary paths. Marine and freshwater fish had large differences in STR content, with the most extreme propagation detected in the genomes of codfish species and Atlantic herring. Such a high density of STRs is likely to increase the mutational load, which we propose could be counterbalanced by high fecundity as seen in codfishes and herring.

• Reinar, William Brynildsen; Greulich, Anne; Stø, Ida Myhrer; Knutsen, Jonfinn Mordekai Blix; Reitan, Trond & Tørresen, Ole K. [Show all 9 contributors for this article] (2023). Adaptive protein evolution through length variation of short tandem repeats in Arabidopsis. Science Advances. 9(12), p. 1–10. doi: 10.1126/sciadv.add6960. Full text in Research Archive Show summary

  Intrinsically disordered protein regions are of high importance for biotic and abiotic stress responses in plants. Tracts of identical amino acids accumulate in these regions and can vary in length over generations because of expansions and retractions of short tandem repeats at the genomic level. However, little attention has been paid to what extent length variation is shaped by natural selection. By environmental association analysis on 2514 length variable tracts in 770 whole-genome sequenced Arabidopsis thaliana, we show that length variation in glutamine and asparagine amino acid homopolymers, as well as in interaction hotspots, correlate with local bioclimatic habitat. We determined experimentally that the promoter activity of a light-stress gene depended on polyglutamine length variants in a disordered transcription factor. Our results show that length variations affect protein function and are likely adaptive. Length variants modulating protein function at a global genomic scale has implications for understanding protein evolution and eco-evolutionary biology.

• Garcia, Lourdes Martinez; Ferrari, Giada; Cuevas, Angelica; Atmore, Lane Margaret; López-Arias, Begoña & Culling, Mark [Show all 18 contributors for this article] (2022). Ancient DNA evidence for the ecological globalization of cod fishing in medieval and post-medieval Europe. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 289(1985). doi: 10.1098/rspb.2022.1107. Full text in Research Archive Show summary

  Understanding the historical emergence and growth of long-range fisheries can provide fundamental insights into the timing of ecological impacts and the development of coastal communities during the last millennium. Whole-genome sequencing approaches can improve such understanding by determining the origin of archaeological fish specimens that may have been obtained from historic trade or distant water. Here, we used genome-wide data to individually infer the biological source of 37 ancient Atlantic cod specimens (ca 1050–1950 CE) from England and Spain. Our findings provide novel genetic evidence that eleventh- to twelfth-century specimens from London were predominantly obtained from nearby populations, while thirteenth- to fourteenth-century specimens were derived from distant sources. Our results further suggest that Icelandic cod was indeed exported to London earlier than previously reported. Our observations confirm the chronology and geography of the trans-Atlantic cod trade from Newfoundland to Spain starting by the early sixteenth century. Our findings demonstrate the utility of whole-genome sequencing and ancient DNA approaches to describe the globalization of marine fisheries and increase our understanding regarding the extent of the North Atlantic fish trade and long-range fisheries in medieval and early modern times.

• Matschiner, Michael; Barth, Julia Maria Isis; Tørresen, Ole K.; Star, Bastiaan; Baalsrud, Helle Tessand & Brieuc, Marine Servane Ono [Show all 10 contributors for this article] (2022). Supergene origin and maintenance in Atlantic cod. Nature Ecology and Evolution. 6(4), p. 469–481. doi: 10.1038/s41559-022-01661-x. Full text in Research Archive Show summary

  Abstract Supergenes are sets of genes that are inherited as a single marker and encode complex phenotypes through their joint action. They are identified in an increasing number of organisms, yet their origins and evolution remain enigmatic. In Atlantic cod, four megabase-scale supergenes have been identified and linked to migratory lifestyle and environmental adaptations. Here we investigate the origin and maintenance of these four supergenes through analysis of whole-genome-sequencing data, including a new long-read-based genome assembly for a non-migratory Atlantic cod individual. We corroborate the finding that chromosomal inversions underlie all four supergenes, and we show that they originated at different times between 0.40 and 1.66 million years ago. We reveal gene flux between supergene haplotypes where migratory and stationary Atlantic cod co-occur and conclude that this gene flux is driven by gene conversion, on the basis of an increase in GC content in exchanged sites. Additionally, we find evidence for double crossover between supergene haplotypes, leading to the exchange of an ~275 kilobase fragment with genes potentially involved in adaptation to low salinity in the Baltic Sea. Our results suggest that supergenes can be maintained over long timescales in the same way as hybridizing species, through the selective purging of introduced genetic variation.

• Guslund, Naomi Croft; Krabberød, Anders Kristian; Nørstebø, Simen Foyn; Solbakken, Monica Hongrø; Jakobsen, Kjetill Sigurd & Johansen, Finn-Eirik [Show all 7 contributors for this article] (2022). Lymphocyte subsets in Atlantic cod (Gadus morhua) interrogated by single-cell sequencing. Communications Biology. 5:689(1), p. 1–9. doi: 10.1038/s42003-022-03645-w. Full text in Research Archive Show summary

  Abstract Atlantic Cod ( Gadus morhua ) has lost the major histocompatibility complex class II presentation pathway. We recently identified CD8-positive T cells, B cells, and plasma cells in cod, but further characterisation of lymphocyte subsets is needed to elucidate immune adaptations triggered by the absence of CD4-positive T lymphocytes. Here, we use single-cell RNA sequencing to examine the lymphocyte heterogeneity in Atlantic cod spleen. We describe five T cell subsets and eight B cell subsets and propose a B cell trajectory of differentiation. Notably, we identify a subpopulation of T cells that are CD8-negative. Most of the CD8-negative T lymphocytes highly express the homologue of monocyte chemotactic protein 1b , and another subset of CD8-negative T lymphocytes express the homologue of the scavenger receptor m130 . Uncovering the multiple lymphocyte cell sub-clusters reveals the different immune states present within the B and T cell populations, building a foundation for further work.

• Sætre, Camilla Lo Cascio; Rönkä, Katja; Ravinet, Mark; Vitulano, Severino; Caldarella, Matteo & Procházka, Petr [Show all 13 contributors for this article] (2022). Genomic consequences of range expansion and colonisation in the reed warbler (Acrocephalus scirpaceus). BioRxiv. ISSN 0362-4331. doi: 10.1101/2022.11.28.518135. Full text in Research Archive
• Garcia, Lourdes Martinez; Ferrari, Giada; Hufthammer, Anne Karin; Jakobsen, Kjetill Sigurd; Jentoft, Sissel & Barrett, James Harold [Show all 7 contributors for this article] (2022). Ancient DNA reveals a southern presence of the Northeast Arctic cod during the Holocene. Biology Letters. ISSN 1744-9561. 18(5). doi: 10.1098/rsbl.2022.0021. Full text in Research Archive Show summary

  Climate change has been implicated in an increased number of distributional shifts of marine species during the last century. Nonetheless, it is unclear whether earlier climatic fluctuations had similar impacts. We use ancient DNA to investigate the long-term spawning distribution of the Northeast Arctic cod (skrei) which performs yearly migrations from the Barents Sea towards spawning grounds along the Norwegian coast. The distribution of these spawning grounds has shifted northwards during the last century, which is thought to be associated with food availability and warming temperatures. We genetically identify skrei specimens from Ruskeneset in west Norway, an archaeological site located south of their current spawning range. Remarkably, 14C analyses date these specimens to the late Holocene, when temperatures were warmer than present-day conditions. Our results either suggest that temperature is not the only driver influencing the spawning distribution of Atlantic cod, or could be indicative of uncertainty in palaeoclimate reconstructions in this region. Regardless, our findings highlight the utility of aDNA to reconstruct the historical distribution of economically important fish populations and reveal the complexity of long-term ecological interactions in the marine environment.

• Nilsson, Pernille; Ravinet, Mark; Cui, Yujun; Berg, Paul Ragnar; Zhang, Yujiang & Guo, Rong [Show all 17 contributors for this article] (2022). Polygenic plague resistance in the great gerbil uncovered by population sequencing. PNAS Nexus. 1(5). doi: 10.1093/pnasnexus/pgac211. Full text in Research Archive
• Dharmarajan, Guha; Li, Ruiyun; Chanda, Emmanuel; Dean, Katharine Rose; Dirzo, Rodolfo & Jakobsen, Kjetill Sigurd [Show all 12 contributors for this article] (2022). The Animal Origin of Major Human Infectious Diseases: What Can Past Epidemics Teach Us About Preventing the Next Pandemic? Zoonoses. ISSN 2737-7474. 2(11). doi: 10.15212/ZOONOSES-2021-0028. Full text in Research Archive
• Taugbøl, Annette; Solbakken, Monica Hongrø; Jakobsen, Kjetill Sigurd & Vøllestad, Leif Asbjørn (2022). Salinity-induced transcriptome profiles in marine and freshwater threespine stickleback after an abrupt 6-hour exposure. Ecology and Evolution. 12(10). doi: 10.1002/ece3.9395. Full text in Research Archive Show summary

  Saltwater and freshwater environments have opposing physiological challenges, yet, there are fish species that are able to enter both habitats during short time spans, and as individuals they must therefore adjust quickly to osmoregulatory contrasts. In this study, we conducted an experiment to test for plastic responses to abrupt salinity changes in two populations of threespine stickleback, Gasterosteus aculeatus, representing two ecotypes (freshwater and ancestral saltwater). We exposed both ecotypes to abrupt native (control treatment) and non- native salinities (0‰ and 30‰) and sampled gill tissue for transcriptomic analyses after 6 h of exposure. To investi-gate genomic responses to salinity, we analyzed four different comparisons; one for each ecotype (in their control and exposure salinity; (1) and (2), one between ecotypes in their control salinity (3), and the fourth comparison included all transcripts identi-fied in (3) that did not show any expressional changes within ecotype in either the control or the exposed salinity (4)). Abrupt salinity transfer affected the expression of 10 and 1530 transcripts for the saltwater and freshwater ecotype, respectively, and 1314 were differentially expressed between the controls, including 502 that were not affected by salinity within ecotype (fixed expression). In total, these results indicate that factors other than genomic expressional plasticity are important for osmoregula-tion in stickleback, due to the need for opposite physiological pathways to survive the abrupt change in salinity. functional genomics, gene expression, osmoregulation, phenotypic plasticity, salinity tolerance, Genetics

• Formenti, Giulio; Theissinger, Kathrin; Fernandes, Carlos; Bista, Iliana; Bombarely, Aureliano & Bleidorn, Christoph [Show all 59 contributors for this article] (2022). The era of reference genomes in conservation genomics. Trends in Ecology & Evolution. ISSN 0169-5347. 37(3), p. 197–202. doi: 10.1016/j.tree.2021.11.008. Full text in Research Archive Show summary

  Progress in genome sequencing now enables the large-scale generation of reference genomes. Various international initiatives aim to generate reference genomes representing global biodiversity. These genomes provide unique insights into genomic diversity and architecture, thereby enabling comprehensive analyses of population and functional genomics, and are expected to revolutionize conservation genomics.

• Lewin, Harris A.; Richards, Stephen; Aiden, Erez Lieberman; Allende, Miguel L.; Archibald, John M. & Bálint, Miklós [Show all 85 contributors for this article] (2022). The Earth BioGenome Project 2020: Starting the clock. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 119(4). doi: 10.1073/pnas.2115635118. Full text in Research Archive
• Kersten, Oliver; Star, Bastiaan; Leigh, Deborah M.; Anker-Nilssen, Tycho; Strøm, Hallvard & Danielsen, Jóhannis [Show all 17 contributors for this article] (2021). Complex population structure of the Atlantic puffin revealed by whole genome analyses. Communications Biology. 4. doi: 10.1038/s42003-021-02415-4. Full text in Research Archive Show summary

  The factors underlying gene flow and genomic population structure in vagile seabirds are notoriously difficult to understand due to their complex ecology with diverse dispersal barriers and extensive periods at sea. Yet, such understanding is vital for conservation management of seabirds that are globally declining at alarming rates. Here, we elucidate the population structure of the Atlantic puffin (Fratercula arctica) by assembling its reference genome and analyzing genome-wide resequencing data of 72 individuals from 12 colonies. We identify four large, genetically distinct clusters, observe isolation-by-distance between colonies within these clusters, and obtain evidence for a secondary contact zone. These observations disagree with the current taxonomy, and show that a complex set of contemporary biotic factors impede gene flow over different spatial scales. Our results highlight the power of whole genome data to reveal unexpected population structure in vagile marine seabirds and its value for seabird taxonomy, evolution and conservation.

• Sætre, Camilla Lo Cascio; Eroukhmanoff, Fabrice; Rönkä, Katja; Kluen, Edward; Thorogood, Rose & Torrance, James [Show all 12 contributors for this article] (2021). A Chromosome-Level Genome Assembly of the Reed Warbler (Acrocephalus scirpaceus). Genome Biology and Evolution (GBE). 13(9), p. 1–7. doi: 10.1093/gbe/evab212. Full text in Research Archive Show summary

  Abstract The reed warbler (Acrocephalus scirpaceus) is a long-distance migrant passerine with a wide distribution across Eurasia. This species has fascinated researchers for decades, especially its role as host of a brood parasite, and its capacity for rapid phenotypic change in the face of climate change. Currently, it is expanding its range northwards in Europe, and is altering its migratory behavior in certain areas. Thus, there is great potential to discover signs of recent evolution and its impact on the genomic composition of the reed warbler. Here, we present a high-quality reference genome for the reed warbler, based on PacBio, 10×, and Hi-C sequencing. The genome has an assembly size of 1,075,083,815 bp with a scaffold N50 of 74,438,198 bp and a contig N50 of 12,742,779 bp. BUSCO analysis using aves_odb10 as a model showed that 95.7% of BUSCO genes were complete. We found unequivocal evidence of two separate macrochromosomal fusions in the reed warbler genome, in addition to the previously identified fusion between chromosome Z and a part of chromosome 4A in the Sylvioidea superfamily. We annotated 14,645 protein-coding genes, and a BUSCO analysis of the protein sequences indicated 97.5% completeness. This reference genome will serve as an important resource, and will provide new insights into the genomic effects of evolutionary drivers such as coevolution, range expansion, and adaptations to climate change, as well as chromosomal rearrangements in birds.

• Pinsky, Malin L.; Eikeset, Anne Maria; Helmerson, Cecilia Jenny Margareta Thomas; Bradbury, Ian R.; Bentzen, Paul & Morris, Corey [Show all 17 contributors for this article] (2021). Genomic stability through time despite decades of exploitation in cod on both sides of the Atlantic. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 118(15). doi: 10.1073/pnas.2025453118. Full text in Research Archive Show summary

  The mode and extent of rapid evolution and genomic change in response to human harvesting are key conservation issues. Although experiments and models have shown a high potential for both genetic and phenotypic change in response to fishing, empirical examples of genetic responses in wild populations are rare. Here, we compare whole-genome sequence data of Atlantic cod (Gadus morhua) that were collected before (early 20th century) and after (early 21st century) periods of intensive exploitation and rapid decline in the age of maturation from two geographically distinct populations in Newfoundland, Canada, and the northeast Arctic, Norway. Our temporal, genome-wide analyses of 346,290 loci show no substantial loss of genetic diversity and high effective population sizes. Moreover, we do not find distinct signals of strong selective sweeps anywhere in the genome, although we cannot rule out the possibility of highly polygenic evolution. Our observations suggest that phenotypic change in these populations is not constrained by irreversible loss of genomic variation and thus imply that former traits could be reestablished with demographic recovery.

• Garcia, Lourdes Martinez; Ferrari, Giada; Oosting, Tom; Ballantyne, Rachel; Jagt, Inge van der & Ystgaard, Ingrid [Show all 20 contributors for this article] (2021). Historical demographic processes dominate genetic variation in ancient Atlantic cod mitogenomes. Frontiers in Ecology and Evolution. 9, p. 1–14. doi: 10.3389/fevo.2021.671281. Full text in Research Archive Show summary

  Ancient DNA (aDNA) approaches have been successfully used to infer the long-term impacts of climate change, domestication, and human exploitation in a range of terrestrial species. Nonetheless, studies investigating such impacts using aDNA in marine species are rare. Atlantic cod (Gadus morhua), is an economically important species that has experienced dramatic census population declines during the last century. Here, we investigated 48 ancient mitogenomes from historical specimens obtained from a range of archeological excavations in northern Europe dated up to 6,500 BCE. We compare these mitogenomes to those of 496 modern conspecifics sampled across the North Atlantic Ocean and adjacent seas. Our results confirm earlier observations of high levels of mitogenomic variation and a lack of mutation-drift equilibrium—suggestive of population expansion. Furthermore, our temporal comparison yields no evidence of measurable mitogenomic changes through time. Instead, our results indicate that mitogenomic variation in Atlantic cod reflects past demographic processes driven by major historical events (such as oscillations in sea level) and subsequent gene flow rather than contemporary fluctuations in stock abundance. Our results indicate that historical and contemporaneous anthropogenic pressures such as commercial fisheries have had little impact on mitogenomic diversity in a wide-spread marine species with high gene flow such as Atlantic cod. These observations do not contradict evidence that overfishing has had negative consequences for the abundance of Atlantic cod and the importance of genetic variation in implementing conservation strategies. Instead, these observations imply that any measures toward the demographic recovery of Atlantic cod in the eastern Atlantic, will not be constrained by recent loss of historical mitogenomic variation.

• Formenti, Giulio & Jakobsen, Kjetill Sigurd (2021). Complete vertebrate mitogenomes reveal widespread repeats and gene duplications. Genome Biology. ISSN 1465-6906. 22. doi: 10.1186/s13059-021-02336-9. Full text in Research Archive
• Reinar, William Brynildsen; Olsson, Vilde; Reitan, Trond; Jakobsen, Kjetill Sigurd & Butenko, Melinka Alonso (2021). Length variation in short tandem repeats affects gene expression in natural populations of Arabidopsis thaliana. The Plant Cell. ISSN 1040-4651. 33(7), p. 2221–2234. doi: 10.1093/plcell/koab107. Full text in Research Archive Show summary

  Abstract The genetic basis for the fine-tuned regulation of gene expression is complex and ultimately influences the phenotype and thus the local adaptation of natural populations. Short tandem repeats (STRs) consisting of repetitive DNA motifs have been shown to regulate gene expression. STRs are variable in length within a population and serve as a heritable, but semi-reversible, reservoir of standing genetic variation. For sessile organisms, such as plants, STRs could be of major importance in fine-tuning gene expression as a response to a shifting local environment. Here, we used a transcriptome dataset from natural accessions of Arabidopsis thaliana to investigate population-wide gene expression patterns in light of genome-wide STR variation. We empirically modeled gene expression as a response to the STR length within and around the gene and demonstrated that an association between gene expression and STR length variation is unequivocally present in the sampled population. To support our model, we explored the promoter activity in a transcriptional regulator involved in root hair formation and provided experimentally determined causality between coding sequence length variation and promoter activity. Our results support a general link between gene expression variation and STR length variation in A. thaliana.

• Ferrari, Giada; Atmore, Lane Margaret; Jentoft, Sissel; Jakobsen, Kjetill Sigurd; Makowiecki, Daniel & Barrett, James [Show all 7 contributors for this article] (2021). An accurate assignment test for extremely low-coverage whole-genome sequence data. Molecular Ecology Resources. ISSN 1755-098X. p. 1–15. doi: 10.1111/1755-0998.13551. Full text in Research Archive Show summary

  Genomic assignment tests can provide important diagnostic biological characteristics, such as population of origin or ecotype. Yet, assignment tests often rely on moderate- to high-coverage sequence data that can be difficult to obtain for fields such as molecular ecology and ancient DNA. We have developed a novel approach that efficiently assigns biologically relevant information (i.e., population identity or structural variants such as inversions) in extremely low-coverage sequence data. First, we generate databases from existing reference data using a subset of diagnostic single nucleotide polymorphisms (SNPs) associated with a biological characteristic. Low-coverage alignment files are subsequently compared to these databases to ascertain allelic state, yielding a joint probability for each association. To assess the efficacy of this approach, we assigned haplotypes and population identity in Heliconius butterflies, Atlantic herring, and Atlantic cod using chromosomal inversion sites and whole-genome data. We scored both modern and ancient specimens, including the first whole-genome sequence data recovered from ancient Atlantic herring bones. The method accurately assigns biological characteristics, including population membership, using extremely low-coverage data (as low as 0.0001x) based on genome-wide SNPs. This approach will therefore increase the number of samples in evolutionary, ecological and archaeological research for which relevant biological information can be obtained.

• Riiser, Even Sannes; Haverkamp, Thomas Hendricus Augustus; Varadharajan, Srinidhi; Borgan, Ørnulf; Jakobsen, Kjetill Sigurd & Jentoft, Sissel [Show all 7 contributors for this article] (2020). Metagenomic Shotgun Analyses Reveal Complex Patterns of Intra- and Interspecific Variation in the Intestinal Microbiomes of Codfishes. Applied and Environmental Microbiology. ISSN 0099-2240. 86(6), p. 1–16. doi: 10.1128/AEM.02788-19. Full text in Research Archive
• Nilsson, Pernille; Solbakken, Monica Hongrø; Schmid, Boris Valentijn; Orr, Russell; Lv, Ruichen & Cui, Yujun [Show all 15 contributors for this article] (2020). The Genome of the Great Gerbil Reveals Species-Specific Duplication of an MHCII Gene. Genome Biology and Evolution (GBE). 12(2), p. 3832–3849. doi: 10.1093/gbe/evaa008. Full text in Research Archive Show summary

  Abstract The great gerbil (Rhombomys opimus) is a social rodent living in permanent, complex burrow systems distributed throughout Central Asia, where it serves as the main host of several important vector-borne infectious pathogens including the well-known plague bacterium (Yersinia pestis). Here, we present a continuous annotated genome assembly of the great gerbil, covering over 96% of the estimated 2.47-Gb genome. Taking advantage of the recent genome assemblies of the sand rat (Psammomys obesus) and the Mongolian gerbil (Meriones unguiculatus), comparative immunogenomic analyses reveal shared gene losses within TLR gene families (i.e., TLR8, TLR10, and the entire TLR11-subfamily) for Gerbillinae, accompanied with signs of diversifying selection of TLR7 and TLR9. Most notably, we find a great gerbil-specific duplication of the MHCII DRB locus. In silico analyses suggest that the duplicated gene provides high peptide binding affinity for Yersiniae epitopes as well as Leishmania and Leptospira epitopes, putatively leading to increased capability to withstand infections by these pathogens. Our study demonstrates the power of whole-genome sequencing combined with comparative genomic analyses to gain deeper insight into the immunogenomic landscape of the great gerbil and its close relatives.

• Cui, Yujun; Schmid, Boris Valentijn; Cao, Hanli; Dai, Xiang; Du, Zhongmin & Easterday, William Ryan [Show all 24 contributors for this article] (2020). Evolutionary selection of biofilm-mediated extended phenotypes in Yersinia pestis in response to a fluctuating environment. Nature Communications. 11, p. 1–8. doi: 10.1038/s41467-019-14099-w. Full text in Research Archive Show summary

  Yersinia pestis is transmitted from fleas to rodents when the bacterium develops an extensive biofilm in the foregut of a flea, starving it into a feeding frenzy, or, alternatively, during a brief period directly after feeding on a bacteremic host. These two transmission modes are in a trade-off regulated by the amount of biofilm produced by the bacterium. Here by investigating 446 global isolated Y. pestis genomes, including 78 newly sequenced isolates sampled over 40 years from a plague focus in China, we provide evidence for strong selection pressures on the RNA polymerase ω-subunit encoding gene rpoZ. We demonstrate that rpoZ variants have an increased rate of biofilm production in vitro, and that they evolve in the ecosystem during colder and drier periods. Our results support the notion that the bacterium is constantly adapting—through extended phenotype changes in the fleas—in response to climate-driven changes in the niche.

• Jin, Xingkun; Morro, Bernat; Tørresen, Ole K.; Moiche, Visila; Solbakken, Monica Hongrø & Jakobsen, Kjetill Sigurd [Show all 8 contributors for this article] (2020). Innovation in Nucleotide-Binding Oligomerization-Like Receptor and Toll-Like Receptor Sensing Drives the Major Histocompatibility Complex-II Free Atlantic Cod Immune System. Frontiers in Immunology. 11. doi: 10.3389/fimmu.2020.609456. Full text in Research Archive
• Croft, Naomi; Solbakken, Monica Hongrø; Brieuc, Marine Servane Ono; Jentoft, Sissel; Jakobsen, Kjetill Sigurd & Qiao, Shuo Wang (2020). Single-Cell Transcriptome Profiling of Immune Cell Repertoire of the Atlantic Cod Which Naturally Lacks the Major Histocompatibility Class II System. Frontiers in Immunology. 11. doi: 10.3389/fimmu.2020.559555. Full text in Research Archive
• Riiser, Even Sannes; Haverkamp, Thomas Hendricus Augustus; Varadharajan, Srinidhi; Borgan, Ørnulf; Jakobsen, Kjetill Sigurd & Jentoft, Sissel [Show all 7 contributors for this article] (2019). Switching on the light: using metagenomic shotgun sequencing to characterize the intestinal microbiome of Atlantic cod. Environmental Microbiology. ISSN 1462-2912. 21(7), p. 2576–2594. doi: 10.1111/1462-2920.14652. Full text in Research Archive Show summary

  Atlantic cod (Gadus morhua) is an ecologically important species with a wide‐spread distribution in the North Atlantic Ocean, yet little is known about the diversity of its intestinal microbiome in its natural habitat. No geographical differentiation in this microbiome was observed based on 16S rRNA amplicon analyses, yet such finding may result from an inherent lack of power of this method to resolve fine‐scaled biological complexity. Here, we use metagenomic shotgun sequencing to investigate the intestinal microbiome of 19 adult Atlantic cod individuals from two coastal populations in Norway–located 470 km apart. Resolving the species community to unprecedented resolution, we identify two abundant species, Photobacterium iliopiscarium and Photobacterium kishitanii, which comprise over 50% of the classified reads. Interestingly, the intestinal P. kishitanii strains have functionally intact lux genes, and its high abundance suggests that fish intestines form an important part of its ecological niche. These observations support a hypothesis that bioluminescence plays an ecological role in the marine food web. Despite our improved taxonomical resolution, we identify no geographical differences in bacterial community structure, indicating that the intestinal microbiome of these coastal cod is colonized by a limited number of closely related bacterial species with a broad geographical distribution.

• Solbakken, Monica Hongrø; Jentoft, Sissel; Reitan, Trond; Mikkelsen, Helene; Jakobsen, Kjetill Sigurd & Seppola, Marit (2019). Whole transcriptome analysis of the Atlantic cod vaccine response reveals subtle changes in adaptive immunity. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 31:100597, p. 1–12. doi: 10.1016/j.cbd.2019.100597. Full text in Research Archive Show summary

  Atlantic cod has lost the Major Histocompatibility complex class II pathway – central to pathogen presentation, humoral response and immunity. Here, we investigate the immunological response of Atlantic cod subsequent to dip vaccination with <i>Vibrio anguillarum</i> bacterin using transcriptome sequencing. The experiment was conducted on siblings from an Atlantic cod family found to be highly susceptible towards vibriosis where vaccination has demonstrated improved pathogen resistance. Gene expression analyses at 2, 4, 21 and 42 days post vaccination revealed GO-term enrichment for muscle, neuron and metabolism-related pathways. In-depth characterization of immune-related GO terms demonstrated down-regulation of MHCI antigen presentation, C-type lectin receptor signaling and granulocyte activation over time. Phagocytosis, interferon-gamma signaling and negative regulation of innate immunity were increasingly up-regulated over time. Individual differentially expressed immune genes implies weak initiation of acute phase proteins with little or no inflammation. Furthermore, gene expression indicates presence of T-cells, NK-like cells, B-cells and monocytes/macrophages. Three <i>MHCI</i> transcripts were up-regulated with <i>B2M</i> and <i>SEC61</i>. Overall, we find no clear immune-related transcriptomic response which could be attributed to Atlantic cod's alternative immune system. However, we cannot rule out that this response is related to vaccination protocol/sampling strategy. Earlier functional studies demonstrate significant memory in Atlantic cod post dip vaccination and combined with our results indicate the presence of other adaptive immunity mechanisms. In particular, we suggest that further investigations should look into CD8+ memory T-cells, γδ T-cells, T-cell independent memory or memory induced through NK-like/other lymphoid cells locally in the mucosal lining for this particular vaccination strategy.

• Musilova, Zuzana; Cortesi, Fabio; Matschiner, Michael; Davies, Wayne I. L.; Patel, Jagdish Suresh & Stieb, Sara M. [Show all 18 contributors for this article] (2019). Vision using multiple distinct rod opsins in deep-sea fishes. Science. ISSN 0036-8075. 364(6440), p. 588–592. doi: 10.1126/science.aav4632. Full text in Research Archive
• Barth, Julia Maria Isis; Villegas-Ríos, David; Freitas, Carla; Moland, Even; Star, Bastiaan & André, Carl [Show all 15 contributors for this article] (2019). Disentangling structural genomic and behavioral barriers in a sea of connectivity. Molecular Ecology. ISSN 0962-1083. 28(6), p. 1394–1411. doi: 10.1111/mec.15010. Full text in Research Archive Show summary

  Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole‐genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord‐type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord‐type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.

• Solbakken, Monica Hongrø; Jentoft, Sissel; Reitan, Trond; Mikkelsen, Helene; Gregers, Tone Fredsvik & Bakke, Oddmund [Show all 8 contributors for this article] (2019). Disentangling the immune response and host-pathogen interactions in Francisella noatunensis infected Atlantic cod. Comparative Biochemistry and Physiology - Part D:Genomics and Proteomics. ISSN 1744-117X. 30, p. 333–346. doi: 10.1016/j.cbd.2019.04.004. Full text in Research Archive Show summary

  The genetic repertoire underlying teleost immunity has been shown to be highly variable. A rare example is Atlantic cod and its relatives Gadiformes that lacks a hallmark of vertebrate immunity: Major Histocompatibility Complex class II. No immunological studies so far have fully unraveled the functionality of this particular immune system. Through global transcriptomic profiling, we investigate the immune response and host-pathogen interaction of Atlantic cod infected with the facultative intracellular bacterium <i>Francisella noatunensis</i>. We find that Atlantic cod displays an overall classic innate immune response with inflammation, acute-phase proteins and cell recruitment through up-regulation of e.g. <i>IL1B</i>, fibrinogen, cathelicidin, hepcidin and several chemotactic cytokines such as the neutrophil attractants <i>CXCL1</i> and <i>CXCL8</i>. In terms of adaptive immunity, we observe up-regulation of interferon gamma followed by up-regulation of several <i>MHCI</i> transcripts and genes related to antigen transport and loading. Finally, we find up-regulation of immunoglobulins and down-regulation of T-cell and NK-like cell markers. Our analyses also uncover some contradictory transcriptional findings such as up-regulation of anti-inflammatory <i>IL10</i> as well as down-regulation of the NADPH oxidase complex and myeloperoxidase. This we interpret as the result of host-pathogen interactions where <i>F. noatunensis</i> modulates the immune response. In summary, our results suggest that Atlantic cod mounts a classic innate immune response as well as a neutrophil-driven response. In terms of adaptive immunity, both endogenous and exogenous antigens are being presented on MHCI and antibody production is likely enabled through direct B-cell stimulation with possible neutrophil help. Collectively, we have obtained novel insight in the orchestration of the Atlantic cod immune system and determined likely targets of <i>F. noatunensis</i> host-pathogen interactions.

• Bråte, Jon; Fuss, Janina; Mehrotra, Shruti; Jakobsen, Kjetill Sigurd & Klaveness, Dag (2019). Draft genome assembly and transcriptome sequencing of the golden algae Hydrurus foetidus (Chrysophyceae). F1000 Research. 8(401), p. 1–12. doi: 10.12688/f1000research.16734.3. Full text in Research Archive Show summary

  Hydrurus foetidus is a freshwater alga belonging to the phylum Heterokonta. It thrives in cold rivers in polar and high alpine regions. It has several morphological traits reminiscent of single-celled eukaryotes, but can also form macroscopic thalli. Despite its ability to produce polyunsaturated fatty acids, its life under cold conditions and its variable morphology, very little is known about its genome and transcriptome. Here, we present an extensive set of next-generation sequencing data, including genomic short reads from Illumina sequencing and long reads from Nanopore sequencing, as well as full length cDNAs from PacBio IsoSeq sequencing and a small RNA dataset (smaller than 200 bp) sequenced with Illumina. We combined this data with, to our knowledge, the first draft genome assembly of a chrysophyte algae. The assembly consists of 5069 contigs to a total assembly size of 171 Mb and a 77% BUSCO completeness. The new data generated here may contribute to a better understanding of the evolution and ecological roles of chrysophyte algae, as well as to resolve the branching patterns within the Heterokonta.

• Varadharajan, Srinidhi; Rastas, Pasi; Löytynoja, Ari; Matschiner, Michael; Calboli, Federico C. F. & Guo, Baocheng [Show all 9 contributors for this article] (2019). A High-Quality Assembly of the Nine-Spined Stickleback (Pungitius pungitius) Genome. Genome Biology and Evolution (GBE). 11(11), p. 3291–3308. doi: 10.1093/gbe/evz240. Full text in Research Archive Show summary

  The Gasterosteidae fish family hosts several species that are important models for eco-evolutionary, genetic and genomic research. In particular, a wealth of genetic and genomic data has been generated for the three-spined stickleback (Gasterosteus aculeatus), the ‘ecology’s supermodel’, while the genomic resources for the nine-spined stickleback (Pungitius pungitius) have remained relatively scarce. Here, we report a high-quality chromosome-level genome assembly of P. pungitius consisting of 5,303 contigs (N50 = 1.2 Mbp) with a total size of 521 Mbp. These contigs were mapped to 21 linkage groups using a high-density linkage map, yielding a final assembly with 98.5% BUSCO completeness. A total of 25,062 protein-coding genes were annotated, and ca. 23% of the assembly was found to consist of repetitive elements. A comprehensive analysis of repetitive elements uncovered centromeric-specific tandem repeats and provided insights into the evolution of retrotransposons. A multigene phylogenetic analysis inferred a divergence time of about 26 million years (MYA) between nine- and three-spined sticklebacks, which is far older than the commonly assumed estimate of 13 MYA. Compared to the three-spined stickleback, we identified an additional duplication of several genes in the hemoglobin cluster. Sequencing data from populations adapted to different environments indicated potential copy number variations in hemoglobin genes. Furthermore, genome-wide synteny comparisons between three- and nine-spined sticklebacks identified chromosomal rearrangements underlying the karyotypic differences between the two species. The high-quality chromosome-scale assembly of the nine-spined stickleback genome obtained with long-read sequencing technology provides a crucial resource for comparative and population genomic investigations of stickleback fishes and teleosts.

• Tørresen, Ole K.; Star, Bastiaan; Mier, Pablo; Andrade-Navarro, Miguel A.; Bateman, Alex & Jarnot, Patryk [Show all 13 contributors for this article] (2019). Tandem repeats lead to sequence assembly errors and impose multi-level challenges for genome and protein databases. Nucleic Acids Research (NAR). ISSN 0305-1048. 47(21), p. 10994–11006. doi: 10.1093/nar/gkz841. Full text in Research Archive Show summary

  The widespread occurrence of repetitive stretches of DNA in genomes of organisms across the tree of life imposes fundamental challenges for sequencing, genome assembly, and automated annotation of genes and proteins. This multi-level problem can lead to errors in genome and protein databases that are often not recognized or acknowledged. As a consequence, end users working with sequences with repetitive regions are faced with ‘ready-to-use’ deposited data whose trustworthiness is difficult to determine, let alone to quantify. Here, we provide a review of the problems associated with tandem repeat sequences that originate from different stages during the sequencing-assembly-annotation-deposition workflow, and that may proliferate in public database repositories affecting all downstream analyses. As a case study, we provide examples of the Atlantic cod genome, whose sequencing and assembly were hindered by a particularly high prevalence of tandem repeats. We complement this case study with examples from other species, where mis-annotations and sequencing errors have propagated into protein databases. With this review, we aim to raise the awareness level within the community of database users, and alert scientists working in the underlying workflow of database creation that the data they omit or improperly assemble may well contain important biological information valuable to others.

• Varadharajan, Srinidhi; Sandve, Simen Rød; Gillard, Gareth Benjamin; Tørresen, Ole K.; Mulugeta, Teshome Dagne & Hvidsten, Torgeir Rhoden [Show all 11 contributors for this article] (2018). The grayling genome reveals selection on gene expression regulation after whole-genome duplication. Genome Biology and Evolution (GBE). 10(10), p. 2785–2800. doi: 10.1093/gbe/evy201. Full text in Research Archive Show summary

  Whole-genome duplication (WGD) has been a major evolutionary driver of increased genomic complexity in vertebrates. One such event occurred in the salmonid family ∼80 Ma (Ss4R) giving rise to a plethora of structural and regulatory duplicate-driven divergence, making salmonids an exemplary system to investigate the evolutionary consequences of WGD. Here, we present a draft genome assembly of European grayling (Thymallus thymallus) and use this in a comparative framework to study evolution of gene regulation following WGD. Among the Ss4R duplicates identified in European grayling and Atlantic salmon (Salmo salar), one-third reflect nonneutral tissue expression evolution, with strong purifying selection, maintained over ∼50 Myr. Of these, the majority reflect conserved tissue regulation under strong selective constraints related to brain and neural-related functions, as well as higher-order protein–protein interactions. A small subset of the duplicates have evolved tissue regulatory expression divergence in a common ancestor, which have been subsequently conserved in both lineages, suggestive of adaptive divergence following WGD. These candidates for adaptive tissue expression divergence have elevated rates of protein coding- and promoter-sequence evolution and are enriched for immune- and lipid metabolism ontology terms. Lastly, lineage-specific duplicate divergence points toward underlying differences in adaptive pressures on expression regulation in the nonanadromous grayling versus the anadromous Atlantic salmon. Our findings enhance our understanding of the role of WGD in genome evolution and highlight cases of regulatory divergence of Ss4R duplicates, possibly related to a niche shift in early salmonid evolution.

• Hoff, Siv Nam Khang; Baalsrud, Helle Tessand; Tooming-Klunderud, Ave; Skage, Morten; Richmond, Todd & Obernosterer, Gregor [Show all 10 contributors for this article] (2018). Long‐read sequence capture of the haemoglobin gene clusters across codfish species. Molecular Ecology Resources. ISSN 1755-098X. 19(1), p. 245–259. doi: 10.1111/1755-0998.12955. Full text in Research Archive
• Riiser, Even Sannes; Haverkamp, Thomas Hendricus Augustus; Borgan, Ørnulf; Jakobsen, Kjetill Sigurd; Jentoft, Sissel & Star, Bastiaan (2018). A single vibrionales 16S rRNA oligotype dominates the intestinal microbiome in two geographically separated Atlantic cod populations. Frontiers in Microbiology. 9. doi: 10.3389/fmicb.2018.01561. Full text in Research Archive Show summary

  Atlantic cod (Gadus morhua) provides an interesting species for the study of host-microbe interactions because it lacks the MHC II complex that is involved in the presentation of extracellular pathogens. Nonetheless, little is known about the diversity of its microbiome in natural populations. Here, we use high-throughput sequencing of the 16S rRNA V4 region, amplified with the primer design of the Earth Microbiome Project (EMP), to investigate the microbial composition in gut content and mucosa of 22 adult individuals from two coastal populations in Norway, located 470 km apart. We identify a core microbiome of 23 OTUs (97% sequence similarity) in all individuals that comprises 93% of the total number of reads. The most abundant orders are classified as Vibrionales, Fusobacteriales, Clostridiales, and Bacteroidales. While mucosal samples show significantly lower diversity than gut content samples, no differences in OTU community composition are observed between the two geographically separated populations. All specimens share a limited number of abundant OTUs. Moreover, the most abundant OTU consists of a single oligotype (order Vibrionales, genus Photobacterium) that represents nearly 50% of the reads in both locations. Our results suggest that these microbiomes comprise a limited number of species or that the EMP V4 primers do not yield sufficient resolution to confidently separate these communities. Our study contributes to a growing body of literature that shows limited spatial differentiation of the intestinal microbiomes in marine fish based on 16S rRNA sequencing, highlighting the need for multi-gene approaches to provide more insight into the diversity of these communities.

• Malmstrøm, Martin; Britz, Ralf; Matschiner, Michael; Tørresen, Ole K.; Hadiaty, Renny Kurnia & Yaakob, Norsham [Show all 10 contributors for this article] (2018). The Most Developmentally Truncated Fishes Show Extensive Hox Gene Loss and Miniaturized Genomes. Genome Biology and Evolution (GBE). 10(4), p. 1088–1103. doi: 10.1093/gbe/evy058. Full text in Research Archive Show summary

  The world’s smallest fishes belong to the genus Paedocypris. These miniature fishes are endemic to an extreme habitat: the peat swamp forests in Southeast Asia, characterized by highly acidic blackwater. This threatened habitat is home to a large array of fishes, including a number of miniaturized but also developmentally truncated species. Especially the genus Paedocypris is characterized by profound, organism-wide developmental truncation, resulting in sexually mature individuals of <8 mm in length with a larval phenotype. Here, we report on evolutionary simplification in the genomes of two species of the dwarf minnow genus Paedocypris using whole-genome sequencing. The two species feature unprecedented Hox gene loss and genome reduction in association with their massive developmental truncation. We also show how other genes involved in the development of musculature, nervous system, and skeleton have been lost in Paedocypris, mirroring its highly progenetic phenotype. Further, our analyses suggest two mechanisms responsible for the genome streamlining in Paedocypris in relation to other Cypriniformes: severe intron shortening and reduced repeat content. As the first report on the genomic sequence of a vertebrate species with organism-wide developmental truncation, the results of our work enhance our understanding of genome evolution and how genotypes are translated to phenotypes. In addition, as a naturally simplified system closely related to zebrafish, Paedocypris provides novel insights into vertebrate development.

• Eide, Marta; Rydbeck, Halfdan; Tørresen, Ole K.; Lille-Langøy, Roger; Puntervoll, Pål & Goldstone, Jared V. [Show all 10 contributors for this article] (2018). Independent losses of a xenobiotic receptor across teleost evolution. Scientific Reports. 8, p. 1–13. doi: 10.1038/s41598-018-28498-4. Full text in Research Archive Show summary

  Sensitivity to environmental stressors largely depend on the genetic complement of the organism. Recent sequencing and assembly of teleost fish genomes enable us to trace the evolution of defense genes in the largest and most diverse group of vertebrates. Through genomic searches and in-depth analysis of gene loci in 76 teleost genomes, we show here that the xenosensor pregnane X receptor (Pxr, Nr1i2) is absent in more than half of these species. Notably, out of the 27 genome assemblies that belong to the Gadiformes order, the pxr gene was only retained in the Merluccidae family (hakes) and Pelagic cod (Melanonus zugmayeri). As an important receptor for a wide range of drugs and environmental pollutants, vertebrate PXR regulate the transcription of a number of genes involved in the biotransformation of xenobiotics, including cytochrome P450 enzymes (CYP). In the absence of Pxr, we suggest that the aryl hydrocarbon receptor (Ahr) have evolved an extended regulatory role by governing the expression of certain Pxr target genes, such as cyp3a, in Atlantic cod (Gadus morhua). However, as several independent losses of pxr have occurred during teleost evolution, other lineages and species may have adapted alternative compensating mechanisms for controlling crucial cellular defense mechanisms.

• Vader, Anna; IV, Haywood Laughinghouse; Griffiths, Colin; Jakobsen, Kjetill Sigurd & Gabrielsen, Tove M. (2018). Proton-pumping rhodopsins are abundantly expressed by microbial eukaryotes in a high-Arctic fjord. Environmental Microbiology. ISSN 1462-2912. 20(2), p. 890–902. doi: 10.1111/1462-2920.14035. Full text in Research Archive
• Jørgensen, Tor Erik; Karlsen, Bård Ove; Emblem, Åse; Breines, Ragna; Andreassen, morten & Rounge, Trine Ballestad [Show all 15 contributors for this article] (2018). Mitochondrial genome variation of Atlantic cod. BMC Research Notes. 11:397, p. 1–7. doi: 10.1186/s13104-018-3506-3. Full text in Research Archive Show summary

  Objective:<br> The objective of this study was to analyse intraspecifc sequence variation of Atlantic cod mitochondrial DNA, based on a comprehensive collection of completely sequenced mitochondrial genomes. <br>Results:<br> We determined the complete mitochondrial DNA sequence of 124 cod specimens from the eastern and western part of the species’ distribution range in the North Atlantic Ocean. All specimens harboured a unique mitochondrial DNA haplotype. Nine hundred and ffty-two polymorphic sites were identifed, including 109 non-synonymous sites within protein coding regions. Eighteen variable sites were identifed as indels, exclusively distributed in structural RNA genes and non-coding regions. Phylogeographic analyses based on 156 available cod mitochondrial genomes did not reveal a clear structure. There was a lack of mitochondrial genetic diferentiation between two ecotypes of cod in the eastern North Atlantic, but eastern and western cod were diferentiated and mitochondrial genome diversity was higher in the eastern than the western Atlantic, suggesting deviating population histories. The geographic distribution of mitochondrial genome variation seems to be governed by demographic processes and gene fow among ecotypes that are otherwise characterized by localized genomic divergence associated with chromosomal inversions.

• Tørresen, Ole K.; Brieuc, Marine Servane; Solbakken, Monica Hongrø; Sørhus, Elin; Nederbragt, Alexander Johan & Jakobsen, Kjetill Sigurd [Show all 9 contributors for this article] (2018). Genomic architecture of haddock (Melanogrammus aeglefinus) shows expansions of innate immune genes and short tandem repeats. BMC Genomics. 19(240), p. 1–17. doi: 10.1186/s12864-018-4616-y. Full text in Research Archive Show summary

  Increased availability of genome assemblies for non-model organisms has resulted in invaluable biological and genomic insight into numerous vertebrates, including teleosts. Sequencing of the Atlantic cod (Gadus morhua) genome and the genomes of many of its relatives (Gadiformes) demonstrated a shared loss of the major histocompatibility complex (MHC) II genes 100 million years ago. An improved version of the Atlantic cod genome assembly shows an extreme density of tandem repeats compared to other vertebrate genome assemblies. Highly contiguous assemblies are therefore needed to further investigate the unusual immune system of the Gadiformes, and whether the high density of tandem repeats found in Atlantic cod is a shared trait in this group.

• Solbakken, Monica Hongrø; Voje, Kjetil L.; Jakobsen, Kjetill Sigurd & Jentoft, Sissel (2017). Linking species habitat and past palaeoclimatic events to evolution of the teleost innate immune system. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 284(1853), p. 1–9. doi: 10.1098/rspb.2016.2810. Full text in Research Archive Show summary

  Host-intrinsic factors as well as environmental changes are known to be strong evolutionary drivers defining the genetic foundation of immunity. Using a novel set of teleost genomes and a time-calibrated phylogeny, we here investigate the family of Toll-like receptor (TLR) genes and address the underlying evolutionary processes shaping the diversity of the first-line defence. Our findings reveal remarkable flexibility within the evolutionary design of teleost innate immunity characterized by prominent TLR gene losses and expansions. In the order of Gadiformes, expansions correlate with the loss of major histocompatibility complex class II (MHCII) and diversifying selection analyses support that this has fostered new immunological innovations in TLRs within this lineage. In teleosts overall, TLRs expansions correlate with species latitudinal distributions and maximum depth. By contrast, lineage-specific gene losses overlap with well-described changes in palaeoclimate (global ocean anoxia) and past Atlantic Ocean geography. In conclusion, we suggest that the evolvability of the teleost immune system has most likely played a prominent role in the survival and successful radiation of this lineage.

• Malmstrøm, Martin; Matschiner, Michael; Tørresen, Ole Kristian; Jakobsen, Kjetill Sigurd & Jentoft, Sissel (2017). Whole genome sequencing data and de novo draft assemblies for 66 teleost species. Scientific Data. 4, p. 1–13. doi: 10.1038/sdata.2016.132. Full text in Research Archive Show summary

  Teleost fishes comprise more than half of all vertebrate species, yet genomic data are only available for 0.2% of their diversity. Here, we present whole genome sequencing data for 66 new species of teleosts, vastly expanding the availability of genomic data for this important vertebrate group. We report on de novo assemblies based on low-coverage (9–39×) sequencing and present detailed methodology for all analyses. To facilitate further utilization of this data set, we present statistical analyses of the gene space completeness and verify the expected phylogenetic position of the sequenced genomes in a large mitogenomic context. We further present a nuclear marker set used for phylogenetic inference and evaluate each gene tree in relation to the species tree to test for homogeneity in the phylogenetic signal. Collectively, these analyses illustrate the robustness of this highly diverse data set and enable extensive reuse of the selected phylogenetic markers and the genomic data in general. This data set covers all major teleost lineages and provides unprecedented opportunities for comparative studies of teleosts.

• Barth, Julia Maria Isis; Berg, Paul Ragnar; Jonsson, Per R; Bonanomi, Sara; Corell, Hanna & Hemmer-Hansen, Jakob [Show all 16 contributors for this article] (2017). Genome architecture enables local adaptation of Atlantic cod despite high connectivity. Molecular Ecology. ISSN 0962-1083. 26(17), p. 4452–4466. doi: 10.1111/mec.14207. Full text in Research Archive Show summary

  Adaptation to local conditions is a fundamental process in evolution; however, mechanisms maintaining local adaptation despite high gene flow are still poorly understood. Marine ecosystems provide a wide array of diverse habitats that frequently promote ecological adaptation even in species characterized by strong levels of gene flow. As one example, populations of the marine fish Atlantic cod (Gadus morhua) are highly connected due to immense dispersal capabilities but nevertheless show local adaptation in several key traits. By combining population genomic analyses based on 12K single nucleotide polymorphisms with larval dispersal patterns inferred using a biophysical ocean model, we show that Atlantic cod individuals residing in sheltered estuarine habitats of Scandinavian fjords mainly belong to offshore oceanic populations with considerable connectivity between these diverse ecosystems. Nevertheless, we also find evidence for discrete fjord populations that are genetically differentiated from offshore populations, indicative of local adaptation, the degree of which appears to be influenced by connectivity. Analyses of the genomic architecture reveal a significant overrepresentation of a large ~5 Mb chromosomal rearrangement in fjord cod, previously proposed to comprise genes critical for the survival at low salinities. This suggests that despite considerable connectivity with offshore populations, local adaptation to fjord environments may be enabled by suppression of recombination in the rearranged region. Our study provides new insights into the potential of local adaptation in high gene flow species within fine geographical scales and highlights the importance of genome architecture in analyses of ecological adaptation.

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• Martin, Sarah Louise; Torre, Renato La; Danneels, Bram; Tooming-Klunderud, Ave; Skage, Morten & Kollias, Spyridon [Show all 12 contributors for this article] (2025). Genome assemblies of four Diamesa species reveal the genetic basis of cold tolerance adaptations and species boundaries. Full text in Research Archive
• Baalsrud, Helle Tessand; Arnyasi, Mariann; To, Thu-Hien; Shapaval, Volha; Byrtusova, Dana & Andersstuen, Terese [Show all 13 contributors for this article] (2025). Chromosomal Chaos: Exploring a Dramatic Shift in the Evolution of Genome Organization in Mucoromycota. Full text in Research Archive
• Reinar, William Brynildsen; Krabberød, Anders Kristian; Lalun, Vilde Olsson; Butenko, Melinka Alonso & Jakobsen, Kjetill Sigurd (2025). Author Correction: Short tandem repeats delineate gene bodies across eukaryotes. Nature Communications. 16(1), p. 1350–1350. doi: 10.1038/s41467-025-56684-2. Full text in Research Archive
• Kersten, Oliver Sven; Garcia, Lourdes Martinez; Pulido, Angélica; Ferrari, Giada; Baalsrud, Helle Tessand & Helmerson, Cecilia [Show all 18 contributors for this article] (2024). Long-term population dynamics of Atlantic cod revealed by Ancient DNA and Genomics. Full text in Research Archive
• Baalsrud, Helle Tessand; Arnyasi, Mariann; To, Thu-Hien; Shapaval, Volha; Byrtusova, Dana & Andersstuen, Terese [Show all 13 contributors for this article] (2024). Different modes of chromosomal evolution in fungi revealed by long-read sequencing. Full text in Research Archive
• Hoff, Siv Nam Khang; Tørresen, Ole Kristian; Maurstad, Marius Filomeno; Ravinet, Mark; Godiksen, Jane Aanestad & Stige, Leif Christian [Show all 10 contributors for this article] (2024). Delineate the population structure of a keystone marine fish species in the Northern Atlantic region using whole genome sequencing data. Full text in Research Archive
• Wargelius, Anna Sofie Troedsson; Hindar, Kjetil & Jakobsen, Kjetill Sigurd (2024). Søknad om forsøksutsetting av genredigert steril laks. Full text in Research Archive
• Hoff, Siv Nam Khang; Maurstad, Marius Filomeno; Alan, Le Moan; Ravinet, Mark; Durant, Joël & Tørresen, Ole K. [Show all 18 contributors for this article] (2023). Identification of multiple chromosomal inversions and fusions in a keystone Arctic species with high gene flow. Full text in Research Archive
• Marcussen, Thomas & Jakobsen, Kjetill Sigurd (2023). En nasjonal dugnad for å kartlegge genomene til alle artene i Norge – EBP-Nor. Biolog. ISSN 0801-0722. 41(1), p. 6–12. Full text in Research Archive
• Hoff, Siv Nam Khang; Maurstad, Marius Filomeno; Moan, Alan Le; Ravinet, Mark; Durant, Joël & Tørresen, Ole Kristian [Show all 18 contributors for this article] (2023). Identification of multiple chromosomal inversions and fusions in a keystone Arctic species with high gene flow. Full text in Research Archive
• Jakobsen, Kjetill Sigurd (2022). Hvorfor genomsekvensere norske arter? doi: https:/www.uio.no/forskning/satsinger/livsvitenskap/livsvitenskapskonferansen/2022/in-life-science/. Full text in Research Archive
• Jakobsen, Kjetill Sigurd (2022). Vi er inne i Livsvitenskapen tidsalder. [Internet]. https://www.tekna.no/kurs/innhold/-vi-er-inne-i-livsvitenskapens-tidsalder/. doi: https:/www.tekna.no/kurs/innhold/-vi-er-inne-i-livsvitenskapens-tidsalder/. Full text in Research Archive
• Tørresen, Ole K.; Baalsrud, Helle Tessand; Sandve, Simen Rød & Jakobsen, Kjetill Sigurd (2022). Bioinfomatic approaches for EBP-Nor. Full text in Research Archive
• Jakobsen, Kjetill Sigurd; Johansen, Finn-Eirik; Qiao, Shuo-Wang; Asdal, Kristin; Druglitrø, Tone & Morsman, Silje Rebecca (2021). Torsken skrotet deler av immunforsvaret. Hva kan vi lære av det? doi: https:/www.aftenposten.no/viten/i/jBR2ko/torsken-skrotet-deler-av-immunforsvaret-hva-kan-vi-laere-av-det. Full text in Research Archive Show summary

  Det er ikke tilfeldig vi går til torsken for å forstå mer av immunsystemet.

• Konstantinidis, Ioannis; Sætrom, Pål; Brieuc, Marine Servane Ono; Jakobsen, Kjetill Sigurd; Liedtke, Hannes & Pohlmann, Caroline [Show all 8 contributors for this article] (2021). DNA hydroxymethylation is linked to higher growth rate in Nile tilapia. Full text in Research Archive
• Stenseth, Nils Christian; Baalsrud, Helle Tessand; Jakobsen, Kjetill Sigurd; Brautaset, Trygve; Goksøyr, Anders & Jensen, Nina [Show all 9 contributors for this article] (2021). Havgenomet – bevaring og bærekraftig bruk av marine genetiske ressurser i Norge. In Rist, Therese & Elvevoll, Edel O. (Ed.), Blått kompass - Stø kurs mot bærekraft i norske havnæringer. Senter for hav og Arktis. ISSN 9788293806080. Full text in Research Archive
• Jakobsen, Kjetill Sigurd; Johansen, Finn-Eirik; Qiao, Shuo Wang; Asdal, Kristin; Druglitrø, Tone & Morsman, Silje Rebecca (2021). Torsken skrotet deler av immunforsvaret. Hva kan vi lære av det? Full text in Research Archive
• Görbitz, Carl Henrik; Jakobsen, Kjetill Sigurd; Sandve, Simen Rød; Goksøyr, Anders; Brautaset, Trygve & Jørgensen, Trond Ø. (2019). Den sjette masseutryddelse og Jordens DNA. Full text in Research Archive
• Jakobsen, Kjetill Sigurd (2019). The Norwegian Initiative for Biodiversity Genomics. Full text in Research Archive
• Tørresen, Ole K.; Skrede, Inger; Sandve, Simen Rød; Jentoft, Sissel; Jakobsen, Kjetill Sigurd & Borge, Ole Johan (2018). Gendykk i norsk natur gir ny kunnskap. Genialt. ISSN 0804-225X. p. 16–18. Full text in Research Archive
• Reinar, William Brynildsen; Tørresen, Ole K.; Matschiner, Michael; Jentoft, Sissel; Nederbragt, Alexander Johan & Jakobsen, Kjetill Sigurd (2018). The impact of repetitive DNA on speciation rates in teleost fish. Full text in Research Archive
• Matschiner, Michael; Star, Bastiaan; Barth, Julia Maria Isis; Jakobsen, Kjetill Sigurd & Jentoft, Sissel (2017). Genomic rearrangements a phylogenetic approach. Full text in Research Archive
• Sandve, Simen Rød; Hvidsten, Torgeir Rhoden; Lien, Sigbjørn; Rori, Rohlfs; Jakobsen, Kjetill Sigurd & Nome, Torfinn [Show all 9 contributors for this article] (2017). Evolution after whole genome duplication - insights from the salmonids. Full text in Research Archive
• Barth, Julia Maria Isis; Star, Bastiaan; Matschiner, Michael; André, Carl; Knutsen, Halvor & Bradbury, Ian [Show all 13 contributors for this article] (2017). Chromosomal rearrangements as barriers to homogenization in highly mobile fish. Full text in Research Archive
• Barth, Julia Maria Isis; Star, Bastiaan; Matschiner, Michael; André, Carl; Knutsen, Halvor & Bradbury, Ian [Show all 13 contributors for this article] (2017). Chromosomal rearrangements as barriers to homogenization in highly mobile fish. Full text in Research Archive
• Skage, Morten; Barth, Julia Maria Isis; Jentoft, Sissel; Øverli, Øyvind & Jakobsen, Kjetill Sigurd (2017). Genetisk bakgrunn hos ulv (Canis lupus) i Norge og Skandinavia. Universitetet i Oslo. Full text in Research Archive Show summary

  Formålet med denne undersøkelsen var å identifisere mulige krysninger mellom hund og ulv i dagens skandinaviske ulvebestand. I tillegg ønsket vi å finne ut i hvor stor grad det er mulig å gjenkjenne innblanding av hund i ulvens arvemateriale (hybridisering og tilbake-krysninger). Metodene som vi har anvendt i undersøkelsen er dyrere og mer tidkrevende enn det dagens forvaltningsmetodikk legger opp til (mikrosatelittanalyse), men gir bedre oppløsning over hele arvemassen og muliggjør deteksjon av svake hybridsignaler. Analysene er basert på data fra hel-genomsekvensering av ulv (dagens skandinaviske bestand og andre ulv), historisk ulv (Nordreisa 1962, Dyrøy 1963, Målselv 1963, og Stor Elvdal 1964), ulvehund (tsjekkisk ulvehund), primitive hunderaser (dingo, basenji, tibetansk mastiff) og moderne hunderaser (boxer etc), alle med ulik geografisk opprinnelse. De norske individene som er sekvensert i denne undersøkelsen kommer alle fra svenske føderevir, men har lagt ut på vandring og blitt avlivet i Norge (Stange, Nord-Odal, Sykkylven, Elverum og Trysil), og inngikk i det som betraktes som en felles skandinavisk bestand. Våre analyser viser: ● Den skandinaviske bestanden grupperer sammen med andre europeiske ulver, og ulver fra Asia, kalt «old world gruppen» i PCA (bilag1) ● Nylig hybridisering mellom ulv og hund ble ikke påvist. ● Genetiske analyser indikerer historisk innblanding av hund i alle analyserte ulver, også i skandinavisk bestand, men det er ikke mer innslag av hund i skandinavisk bestand enn hva som er funnet i andre populasjoner.

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