Unravelling Wood Extractive Resistance in Phanerochaete chrysosporium Through Random Mutagenesis.

During wood degradation, fungi have to deal with toxic and stressful compounds called wood extractives. The identification of the various detoxification strategies developed by fungi, and the molecular targets of these compounds is limited in Basidiomycetes because of the lack of genetic tools. To circumvent this problem, we have developed a direct genetic strategy in the white-rot fungus Phanerochaete chrysosporium. A library of P. chrysosporium UV mutants was generated and screened to isolate mutants resistant to Bagassa guianensis wood extractives (BWE). Wood extractives contribute to B. guianensis wood durability, and resistance to those extractives confers to the mutants a better ability to mineralise wood sawdust. This resistance phenotype is due to causal mutation(s) in the gene coding for an ortholog of the human DENND6, a protein involved in endocytic recycling. Using in silico and in vivo assays, we identified that moracin N, found in BWE, has antifungal activity likely by binding onto the wild type PcDENND6 protein but not onto the mutated variant.