The molecular response of the white-rot fungus Dichomitus squalens to wood and non-woody biomass as examined by transcriptome and exoproteome analyses

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. Overall design: This study compares the gene expression of D. squalens growing on different plant biomass at two different time points. The culture medium was supplemented with spruce wood (Picea abies) sawdust, aspen wood (Populus tremula) sawdust, powdered wheat bran or powdered cotton seed hulls respectively. Samples were taken after 9 and 16 days of culture.