Rme1: Unveiling a Novel Repressor in the Cellulolytic Pathway of Trichoderma reesei.

Thefilamentous fungus Trichoderma reesei is renowned for its exceptional ability to secrete cellulolytic enzymes, which play a crucial role in the hydrolysis of lignocellulose biomass. The expression of fungal cellulases is meticulously regulated at the transcriptional level, depending on the carbon source available in the medium. To obtain new insights into the transcriptional network controlling cellulase expression in T. reesei, we analyzed RNA-Seq data and identified and characterized a new transcription factor, Rme1, that regulates the expression of cellulolytic genes. Combining functional genomics and protein-DNA interaction assay, we showed that Rme1 acts as a repressor of cellulase production in T. reesei by directly regulating two critical genes involved in cellulose degradation: the cellobiohydrolase cel7a and the carbon catabolite repressor cre1. This is the first report of a transcription factor regulating Cre1. This study contributes to a better understanding of the complex regulation of the cellulolytic system of T. reesei and may be useful for the genetic modification of strains for the biorefinery industry.