Effects of VPS13 deletion on hyphal branch, sporulation and cellulase production in Trichoderma reesei

Abstract:

[Objective] Trichoderma reesei is one of the major industrial fungi for cellulase production. A large amount of cellulases are secreted from the fungal cell through the protein secretion pathway. Therefore, knowledge of specific gene functions related to protein secretion would contribute to identification of key factors controlling cellulase production. In this study, the vacuolar protein sorting-associated gene VPS13 was deleted by gene knockout strategy in T. reesei and effects of VPS13 deletion on fungal growth and cellulase production were analyzed.[Methods] Double-joint PCR technique and homologous recombination method were used to delete VPS13 gene in T. reesei QP4 strain. Fungal cultivation, microscopic observation, sporulation detection, protein content and enzyme activity determination were applied to compare the growth characteristics, morphology, spore formation, and cellulase activity between the deletion strains and the parental strain.[Results] Two VPS13 deletion strains, ΔVPS13-1 and ΔVPS13-2, were obtained successfully. Compared with the parental strain, the mutants showed slower hyphae spreading, but their biomass increased significantly after the logarithmic growth phase. In addition, VPS13 deletion led to delay of sporulation. Cellulose plate cultivation revealed that VPS13 mutants produced clearer transparent halos around colonies than the parental strain, indicating that VPS13 deletion increased the ability to degrade cellulose. Furthermore, liquid fermentation showed that VPS13 deletion also improved protein yield and cellulase activity.[Conclusion] T. reesei VPS13 gene can be used as an important target to improve cellulase yield.