Project description:The ability to obtain carbon and energy is a major requirement to exist in any environment. For several ascomycete fungi (post-)genomic analyses have shown that species that occupy a large variety of habitats possess a diverse enzymatic machinery, while species with a specific habitat have a more focused enzyme repertoire that is well-adapted to the prevailing substrate. White-rot basidiomycete fungi also live in a specific habitat, as they are found exclusively in wood. In this study we evaluated how well the white-rot fungus Dichomitus squalens has adapted to degrade its natural wood substrate. The transcriptome and exoproteome of D. squalens were analysed after cultivation on two natural substrates, aspen and spruce wood, and two non-woody substrates, wheat bran and cotton seed hulls. D. squalens produced ligninolytic enzymes mainly at the early time point of the wood cultures, indicating the need to degrade lignin to get access to wood polysaccharides. Surprisingly, the response of the fungus to the non-woody polysaccharides was nearly as good match to the substrate composition as observed for the wood polysaccharides. This indicates that D. squalens has preserved its ability to efficiently degrade plant polysaccharides not present in its natural habitat.
Project description:Carbon catabolite repression (CCR) occurs in the presence of sufficient concentrations of easy metabolizable carbon sources (e.g. glucose), down-regulating the expression of genes encoding enzymes involved in the breakdown of complex carbon sources. The extent of CCR at a global level is unknown in wood-rotting fungi – and was investigated in Dichomitus squalens with transcriptomics and exo-proteomics. Approximately 10% of expressed genes had lower expression in presence of glucose compared to Avicel or xylan alone. The glucose repressed genes included key components for utilization of plant biomass – CAZymes, sugar transporters and carbon catabolic genes. The majority of polysaccharide degrading CAZymes were repressed and included activities towards all major polymers. The repression found in the transcriptome was strongly supported by exo-proteomics – there was repression of almost all of the CAZymes whose transcripts were repressed on Avicel. The clear CCR-mediated effects indicate biotech production of CAZymes by D. squalens would benefit from de-repressed or constitutively expressing strains. The extent of CCR is surprising given that D. squalens rarely experiences high sugar concentrations in its woody environment.
