Introduction of the Aspergillus fumigatus α-1,2-mannosidase MsdS into Trichoderma reesei leads to abnormal polarity and improves the ligno-cellulose degradation

Abstract

-1,2-Mannosidase is an important enzyme essential for N-glycan processing and plays a significant role in the biosynthesis and organization of fungal cell wall. Lacking of -1,2-mannosidase leads to cell wall defect in yeast and filamentous fungi. Trichoderma reesei is known to be non-toxic to human, and its N-glycan on secreted glycoprotein is Man8GlcNAc2. To evaluate the significance of the N-glycan processing in T. reesei, in this study Aspergillus fumigatus -1, 2-mannosidase MsdS, an enzyme that cleaves N-linked Man8GlcNAc2 in Golgi to produce Man6GlcNAc2 on secreted glycoprotein, was introduced into T. reesei. The msdS-expressing strain Tr-MsdS produced a major glycoform of Man6GlcNAc2 on its secreted glycoproteins, instead of Man8GlcNAc2 in the parent strain. Although the cell wall content of msdS-expressing strain Tr-MsdS was changed, it appeared that the cell wall integrity was not affected. However, phenotypes such as increased conidiation, multiple budding and random branching were observed in strain Tr-MsdS. In addition, expression of MsdS into T. ressei also affected protein secretion and improved the ligno-cellulose degradation of T. reesei. Our results indicate that processing of the N-glycan is species-specific and plays an important role in protein secretion in T. reesei, specially cellulases. Also, our results provide a new strategy to improve cellulases production by interfering the N-glycan processing in T. reesei. ImportanceFor the first time, the N-glycan processing is shown to play an important role in polarized growth and protein secretion in T. reesei. In addition, our results show that alterated N-glycan processing enhances cellulose degradation, which provides a strategy to improve cellulases production in T. reesei.