PCR-MEDIATED ANALYSIS OF LIGNOCELLULOLYTIC GENE-TRANSCRIPTION BY PHANEROCHAETE-CHRYSOSPORIUM - SUBSTRATE-DEPENDENT DIFFERENTIAL EXPRESSION WITHIN GENE FAMILIES

We compare the kinetics of appearance of supernatant enzyme activities (lignin peroxidase, manganese peroxidase, and cellulase) and gene exp ression (LIG, mnp, and cbhI gene families and the unique cbhII gene) i n Phanerochaete chrysosporium ME446 when grown on four different carbo n sources: hall-milled straw, representing the natural substrate ligno cellulose; Avicel as a crystalline cellulose; and high and low concent rations of glucose, in all cases with limiting nitrogen. PCR-based tec hnology utilizing pairs of primers specific for particular genes showe d that there is differential expression between and within the familie s. There were a number of instances of mRNA species being present only on a single day, implying tight regulation of lignocellulose degradat ion at the mRNA level. The patterns of extracellular enzyme activities and mnp and cbh gene expression are similar whereas LIG gene expressi on can be detected when no corresponding enzyme activity is observed i n the extracellular supernatant. The enzyme produced under these condi tions is presumably sequestered by the mycelium and is likely to be fu nctionally significant. Another striking result is that cellulose, in the form of Avicel, elicits the expression of three LIG genes for whic h there is no expression under the same conditions with the other carb on sources.