Transcriptional regulation of laccase and cellulase in relation to fruit body formation in the mycelium of Lentinula edodes on a sawdust-based substrate

Extracellular enzyme activities of laccase and cellulase and their transcriptional regulation were investigated at various growth stages in a sawdust-based substrate for Lentinula edodes. Changes of laccase and cellulase activities revealed a clear relationship with fruit body development stages. Laccase and cellulase activities were regulated at the level of gene transcription. The level of laccase mRNA was maximal at the fully colonized stage and declined during fruit body development. Cellulase mRNA began to accumulate at the pin (miniature fruit bodies) formation stage. Cellulase mRNA transcripts were maximally expressed at the veil-break stage of fruit body development. This tendency was clearer in the fruiting cultures with the wide-range-weather strains than in non-fruiting cold-weather strains. Transcription of laccase and cellulase genes was also affected by the water conditions of the sawdust-based substrate. Primordia initiation occurred when the water potential of the medium was high for rapid mRNA transcription by the mycelium.