Functional characterization of endo-β-1,3-glucanase in Trichoderma reesei

While endo-β-1,3-glucanases, crucial for hydrolyzing β-1,3-glucan in cell wall, play significant roles in cellular activities of filamentous fungi, research on these enzymes in Trichoderma reesei remains scarce. In this study, we explored the cellular functions and molecular properties of a novel endo-β-glucanase, GLU1, in T. reesei. The mRNA level of glu1 was noticeably upregulated under cellulase-producing condition as compared to non-cellulase-producing condition. Moreover, the deletion of glu1 significantly repressed cellulase production, primarily by reducing the transcript levels of key genes involved in cellulase synthesis during the early stages of fermentation. This deletion further led to weakened cell growth, diminished sporulation, and mutated colony morphology. These suggest that glu1 plays a crucial positive role in cellulase biosynthesis, cell growth, and sporulation. Additionally, the absence of glu1 led to increased β-glucan content within cell wall, making T. reesei more susceptible to Congo red but less sensitive to NaCl. This suggests that GLU1 is involved in modulating the composition and functionality of cell wall. Bioinformatic analyses classified GLU1 within the GH64 family, while the cellular distribution analysis revealed GLU1 was located in the cytoplasm. These experimental data broaden our understanding of the roles and molecular characteristics of endo-β-1,3-glucanases in filamentous fungi.