Integration of chemosensing and carbon catabolite repression impacts fungal enzyme regulation and plant associations

Fungal metabolism and enzyme production are regulated by nutrient availability and by interactions with the living environment. We investigated the mechanisms underpinning adaptation of the biotechnological fungus Trichoderma reesei to decaying plant biomass versus living plants. We found that concentration-gated response to glucose, the main molecule sensed from dead plant biomass, is mediated by a conserved signaling pathway downstream of G protein-coupled receptors (GPCRs), while the carbon catabolite repressor CRE1 is critical for glucose concentration gating. The GPCRs CSG1 and CSG2 are further required for root colonization and formation of appressorium like structures on plant surfaces. Acceleration of sexual development in the presence of plant roots and their interactions with fruiting bodies indicates preferential association with plants. Our results reveal a complex sensing network governing resource distribution, enzyme production and fungal development that explains previously observed phenomena in fermentations and opens new perspectives for industrial strain improvement and agriculture.