Dehydrogenase GRD1 Represents a Novel Component of the Cellulase Regulon in Trichoderma reesei (Hypocrea jecorina)

Trichoderma reesei (Hypocrea jecorina ) is nowadays the most important industrial producer of cellulase and hemicellulase enzymes, which are used for pretreatment of cellulosic biomass for biofuel production. In this study, we introduce a novel component, GRD1 (glucose-ribitol dehydrogenase 1), which shows enzymatic activity on cellobiose and positively influences cellulase gene transcription, expression, and extracellular endo-1,4-β-d -glucanase activity.grd1 is differentially transcribed upon growth on cellulose and the induction of cellulase gene expression by sophorose. The transcription ofgrd1 is coregulated with that ofcel7a (cbh1 ) under inducing conditions. GRD1 is further involved in carbon source utilization on several carbon sources, such as those involved in lactose andd -galactose catabolism, in several cases in a light-dependent manner. We conclude that GRD1 represents a novel enhancer of cellulase gene expression, which by coregulation with the major cellulase may act via optimization of inducing mechanisms.