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• Trigo, Sergio Galindo; Khandare, Virendrasinh; Roosjen, Mark; Adams, Julian; Wangler, Alexa-Maria & Bayer, Martin [Show all 9 contributors for this article] (2024). A multifaceted kinase axis regulates plant organ abscission through conserved signaling mechanisms. Current Biology. ISSN 0960-9822. 34(13), p. 3020–3030. doi: 10.1016/j.cub.2024.05.057. Full text in Research Archive Show summary

  Plants have evolved mechanisms to abscise organs as they develop or when exposed to unfavorable conditions.1 Uncontrolled abscission of petals, fruits, or leaves can impair agricultural productivity.2,3,4,5 Despite its importance for abscission progression, our understanding of the IDA signaling pathway and its regulation remains incomplete. IDA is secreted to the apoplast, where it is perceived by the receptors HAESA (HAE) and HAESA-LIKE2 (HSL2) and somatic embryogenesis receptor kinase (SERK) co-receptors.6,7,8,9 These plasma membrane receptors activate an intracellular cascade of mitogen-activated protein kinases (MAPKs) by an unknown mechanism.10,11,12 Here, we characterize brassinosteroid signaling kinases (BSKs) as regulators of floral organ abscission in Arabidopsis. BSK1 localizes to the plasma membrane of abscission zone cells, where it interacts with HAESA receptors to regulate abscission. Furthermore, we demonstrate that YODA (YDA) has a leading role among other MAPKKKs in controlling abscission downstream of the HAESA/BSK complex. This kinase axis, comprising a leucine-rich repeat receptor kinase, a BSK, and an MAPKKK, is known to regulate stomatal patterning, early embryo development, and immunity.10,13,14,15,16 How specific cellular responses are obtained despite signaling through common effectors is not well understood. We show that the identified abscission-promoting allele of BSK1 also enhances receptor signaling in other BSK-mediated pathways, suggesting conservation of signaling mechanisms. Furthermore, we provide genetic evidence supporting independence of BSK1 function from its kinase activity in several developmental processes. Together, our findings suggest that BSK1 facilitates signaling between plasma membrane receptor kinases and MAPKKKs via conserved mechanisms across multiple facets of plant development.

• Trigo, Sergio Galindo; Bågman, Anne-Maarit; Ishida, Takashi; Sawa, Shinichiro; Brady, Siobhán M. & Butenko, Melinka Alonso (2024). Dissection of the IDA promoter identifies WRKY transcription factors as abscission regulators in Arabidopsis. Journal of Experimental Botany. ISSN 0022-0957. 75(8), p. 2417–2434. doi: 10.1093/jxb/erae014. Full text in Research Archive Show summary

  Plants shed organs such as leaves, petals, or fruits through the process of abscission. Monitoring cues such as age, resource availability, and biotic and abiotic stresses allow plants to abscise organs in a timely manner. How these signals are integrated into the molecular pathways that drive abscission is largely unknown. The INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) gene is one of the main drivers of floral organ abscission in Arabidopsis and is known to transcriptionally respond to most abscission-regulating cues. By interrogating the IDA promoter in silico and in vitro, we identified transcription factors that could potentially modulate IDA expression. We probed the importance of ERF- and WRKY-binding sites for IDA expression during floral organ abscission, with WRKYs being of special relevance to mediate IDA up-regulation in response to biotic stress in tissues destined for separation. We further characterized WRKY57 as a positive regulator of IDA and IDA-like gene expression in abscission zones. Our findings highlight the promise of promoter element-targeted approaches to modulate the responsiveness of the IDA signaling pathway to harness controlled abscission timing for improved crop productivity.

• Lalun, Vilde Olsson; Breiden, Maike; Trigo, Sergio Galindo; Smakowska-Luzan, Elwira; Simon, Rüdiger & Butenko, Melinka Alonso (2023). A dual function of the IDA peptide in regulating cell separation and modulating plant immunity at the molecular level. eLIFE. 12, p. 1–37. doi: 10.7554/eLife.87912.1. Full text in Research Archive Show summary

  The abscission of floral organs and emergence of lateral roots in Arabidopsis is regulated by the peptide ligand INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) and the receptor protein kinases HAESA (HAE) and HAESA-LIKE 2 (HSL2). During these cell separation processes, the plant induces defense-associated genes to protect against pathogen invasion. However, the molecular coordination between abscission and immunity has not been thoroughly explored. Here we show that IDA induces a receptor-dependent release of cytosolic calcium ions (Ca2+) and apoplastic production of reactive oxygen species, which are signatures of early defense responses. In addition, we find that IDA promotes late defense responses by the transcriptional upregulation of genes known to be involved in immunity. When comparing the IDA induced early immune responses to known immune responses, such as those elicited by flagellin22 treatment, we observe both similarities and differences. We propose a molecular mechanism by which IDA promotes signatures of an immune response in cells destined for separation to guard them from pathogen attack.

• Alling, Renate & Trigo, Sergio Galindo (2023). Reproductive defects in the abscission mutant ida-2 are caused by T-DNA-induced genomic rearrangements. Plant Physiology. ISSN 0032-0889. 193(4), p. 2292–2297. doi: 10.1093/plphys/kiad449. Full text in Research Archive
• Trigo, Sergio Galindo; Grand, Thomas M.; Voigt, Christian A. & Smith, Lisa M. (2020). A malectin domain kinesin functions in pollen and seed development in Arabidopsis. Journal of Experimental Botany. ISSN 0022-0957. 71(6), p. 1828–1841. doi: 10.1093/jxb/eraa023. Full text in Research Archive
• Trigo, Sergio Galindo; Blanco-Tourinan, Noel; DeFalco, Thomas A; Wells, Eloise S; Gray, Julie E & Zipfel, Cyril [Show all 7 contributors for this article] (2020). CrRLK1L receptor‐like kinases HERK1 and ANJEA are female determinants of pollen tube reception. EMBO Reports. ISSN 1469-221X. 21(2), p. 1–18. doi: 10.15252/embr.201948466. Full text in Research Archive Show summary

  Communication between the gametophytes is vital for angiosperm fertilisation. Multiple CrRLK1L‐type receptor kinases prevent premature pollen tube burst, while another CrRLK1L protein, FERONIA (FER), is required for pollen tube reception in the female gametophyte. We report here the identification of two additional CrRLK1L homologues, HERCULES RECEPTOR KINASE 1 (HERK1) and ANJEA (ANJ), which act redundantly to promote pollen tube growth arrest at the synergid cells. HERK1 and ANJ localise to the filiform apparatus of the synergid cells in unfertilised ovules, and in herk1 anj mutants, a majority of ovules remain unfertilised due to pollen tube overgrowth, together indicating that HERK1 and ANJ act as female determinants for fertilisation. As in fer mutants, the synergid cell‐specific, endomembrane protein NORTIA (NTA) is not relocalised after pollen tube reception; however, unlike fer mutants, reactive oxygen species levels are unaffected in herk1 anj double mutants. Both ANJ and HERK1 associate with FER and its proposed co‐receptor LORELEI (LRE) in planta. Together, our data indicate that HERK1 and ANJ act with FER to mediate female–male gametophyte interactions during plant fertilisation. Made available in DUO with special permission from EMBO Press.

• Trigo, Sergio Galindo; Blümke, Patrick; Simon, Rüdiger & Butenko, Melinka Alonso (2020). Emerging mechanisms to fine-tune receptor kinase signaling specificity. Current opinion in plant biology. ISSN 1369-5266. 57, p. 41–51. doi: 10.1016/j.pbi.2020.05.010. Full text in Research Archive Show summary

  Organisms need to constantly inform their cellular machinery about the biochemical and physical status of their surroundings to adapt and thrive. While some external signals are also sensed intracellularly, a considerable share of external information is registered already at the plasma membrane (PM). Receptor kinases (RKs) are crucial for plant cells to integrate such cues from the environment, from microbes, or from other cells to coordinate their physiological response and their development. Early studies on RK signaling depicted the path from external signal to internal response in a linear fashion, but recent findings show that these cellular information highways are highly interconnected and pass signals through molecular intersections. In this review, we first discuss how individual RKs simultaneously contribute to the transduction and deconvolution of a multitude of signals by controlled assembly into diverse RK complexes, exemplified by FERONIA signaling versatility. We then elaborate on how cells can exert highly localized control over the assembly, interaction and composition of such complexes in order to attain essential cellular output specificity.

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• Trigo, Sergio Galindo (2023). Parents, time, and space: The three dimensions of endosperm gene expression. Plant Physiology. ISSN 0032-0889. 191(2), p. 828–830. doi: 10.1093/plphys/kiac566. Full text in Research Archive
• Trigo, Sergio Galindo (2022). Cool (soy)beans! SMV RESISTANCE CLUSTER7 protects plants against viruses. 188(2), p. 934–936. doi: 10.1093/plphys/kiab521. Full text in Research Archive
• Trigo, Sergio Galindo (2022). STARTing to dissect the molecular determinants of GLABRA2 activity. 190(4), p. 2064–2065. doi: 10.1093/plphys/kiac436. Full text in Research Archive
• Trigo, Sergio Galindo (2021). A balancing act: the role of a lectin receptor kinase in determining seed size and quantity. 187(1), p. 21–23. doi: 10.1093/plphys/kiab318. Full text in Research Archive
• Trigo, Sergio Galindo (2021). Two genotypes, one phenotype? The roles of CBP60b during immunity. 186(3), p. 1371–1372. doi: 10.1093/plphys/kiab210. Full text in Research Archive

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