TSC2 is a positive master regulator of cellulase production by affecting protein secretion in Trichoderma reesei

Understanding the molecular mechanism behind fungal cellulase production is key to enhancing cellulase production, but the relevant signaling pathways are yet to be explored. This study elucidates TSC2 as a positive master regulator of cellulase production in Trichoderma reesei. Genetic deletion of tsc2 severely impaired cellulase secretion, particularly under cellulose induction. The mTOR inhibitor Torin 1 significantly inhibited the production of CMC and BGL at the early stage. Torin 1-mediated mTORC1 inhibition partially restored CMC and BGL production in ΔTSC2, linking hyperactive mTORC1 to secretion suppression in ΔTSC2. Transcriptomic analysis of ΔTSC2 revealed significant dysregulation of non-classical secretion genes and autophagy-related genes. GRASP55 knockout phenocopied ΔTSC2 defects, impairing cellulase activity and secretion, while altering autophagy gene expression. Autophagy inhibition via ammonium chloride or atg8 deletion suppressed cellulase yields. These findings suggest that the TSC2-mTORC1-GRASP55-autophagy signaling axis may govern the secretion of cellulase components BGL and CMC, playing a crucial role in cellulase production in T. reesei.