Complex regulation of hydrolytic enzyme genes for cellulosic biomass degradation in filamentous fungi.

Filamentous fungi produce cellulolytic and hemicellulolytic enzymes in response to small inducer molecules liberated from cellulosic biomass. Enzyme production is mainly regulated at the level of transcription. The first transcription factor identified as being involved in cellulosic biomass degradation was XlnR, which mediates D-xylose-triggered induction of xylanolytic and cellulolytic genes in Aspergillus. XlnR has played the leading role for over a decade in studies aimed at clarification of gene regulation related to cellulosic biomass degradation. Very recently, several new transcription factors were identified, namely Clr-1/2 in Neurospora; ManR, McmA, and ClbR in Aspergillus; and BglR in Trichoderma, all of which participate in the regulation of cellulolytic and/or hemicellulolytic enzyme production. Furthermore, as well as the carbon sources available, other factors such as light signaling and anti-sense RNA accumulation have been shown to contribute to this regulation. Here, we review the recent advancements demonstrating that multiple factors coordinately regulate the expression of cellulosic biomass degrading enzyme genes.