The genomic and physiological basis of invasiveness in a harmful house-invader (InHouse)
Serpula lacrymans in natural and artificial environment.
Photo: Mycoteam, Inger Skrede and Håvard Kauserud
Summary: The dry rot fungus, Serpula lacrymans (Serpulaceae, Boletales), is the most aggressive fungus decomposing buildings in temperate regions worldwide. The species has invaded Europe and Japan independently from its native range in central Asia. We are investigating the genetic, expressional and physiological basis for the success of the fungus as an invader of human-made wood constructions. We hypothesize that 1) genetic diversity in the invasive population is important in order to be an efficient invader, 2) that the gene expression of certain genetic pathways, e.g. translocation proteins, will be important to tolerate the semi-arid and nutrient-patchy habitat inside houses, 3) that genes have been lost in relation to stress and temperature tolerance in the house invading strains, and 4) that the house-invading strains are inferior biological competitors in the wild in their founder areas. We have sequenced the genomes of Serpula lacrymans strains of the different invasions and the wild relative, Serpula lacrymans var. shastensis. We are manipulating the growth conditions of these strains and are sequencing RNA from these different growth conditions. Preliminary results indicate that the genetic diversity is larger in the Japanese population, and that the Japanese population is more efficient in decomposing wood than the European population. We expect to obtain further knowledge of the changes accompanying the transition from the wild into houses, and the role of gene expression in brown rot decomposition.
The main objectives of the InHouse project:
1) Which genetic factors are important for invasiveness in S. lacrymans? This question will be investigated by comparing genome sequences, gene expression data and the physiology of eight invasive and non-invasive strains of var. lacrymans (aggressive) and var. shastensis (nonaggressive). We will do re-sequencing for genome comparisons and search for differences in protein coding gene content, promoter changes, selective pressure, heterozygosity, and repetitive DNA. In addition, we will focus on the following major genetic pathways and expression patterns: i) drought and stress related factors, ii) genetic factors related to temperature constraints, iii) loss of cellulose decomposition enzymes like hydrolytic carbohydrate active enzymes and oxidoreductase enzymes, in addition to genetic factors related to the Fenton reaction, iv) genetic patterns associated with transport of nutrients and the formation of rhizomorphs. The sister species Serpula himantioides will be used as outgroup for these analyses.
2) Which physiological characteristics have been important for the transition from the wild into houses? The physiological characteristics of indoor strains to will be compared to cultures of var. shastensis from nature. We will link the differences in physiology to the genetic properties and specific genetic pathways studied in point 1. 3) What is the impact of genetic variation for invasiveness? We will investigate the effect of genetic variation of invasive species by comparing the aggressiveness and decomposition ability of the two different invasive populations (Japan and Europe) and their hybrid.
4) Why is S. lacrymans restricted to buildings in founder areas? We want to address why S. lacrymans is bound to buildings in founder populations and does not appear as an invasive species in nature. The understanding of why the species is restricted to buildings will also provide information about which properties that makes buildings a suitable habitat.
The project is funded by the Norwegian Research Council, grant number 225043