Quantitative linkage mapping of lignin-degrading enzymatic activities in Pleurotus ostreatus

Pleurotus ostreatus and Phanerochaete chrysosporium are two model lignin-degrading basidiomycetes. The genome of P. chrysosporium has been released and that of P. ostreatus will be available soon. The lignin-degrading strategies of these two fungi are, however, different as P. ostreatus lacks lignin peroxidases (LiP) whereas P. chrysosporium lacks phenol oxidases (Pox). Both fungi, in addition, contain genes coding for Mn-oxidizing peroxidases [manganese (MnP) and versatile (VP) peroxidases in P. ostreatus (mnp genes), and manganese peroxidases in P. chrysosporium]. We have mapped genetically the genes coding for different ligninolytic enzymes in P. ostreatus and we have found them linked to chromosomes IV (mnp1, VP activity), V (mnp3, MnP activity) and VI (mnp2, VP activity; pox1 and poxC, Pox activity). If the enzymatic activities are mapped as quantitative traits instead of mapping the structural genes, the genome regions containing regulators of these activities will be detected in addition to the structural genes. We have used this approach for the Pox and MnP/VP activities and we have identified various genomic regions that control them and that map to linkage groups different from those where the corresponding structural genes had been previously mapped to. These new sites could code for regulatory genes. Using a combination of this information and classic genetic techniques, we have selected new P. ostreatus strains enriched in specific activities while maintaining a low biomass production in submerged cultures.