The β-1,6-glucanase MoGlu16 is Required for Mycelia Growth and Pathogenicity of Magnaporthe oryzae

Fungal cell wall is essential in orchestrating fungal morphogenesis and sensing environmental stimuli. Its dynamic reconstruction involves glycoside hydrolases, particularly β-1,6-glucanase, which is crucial for synthesis of β-1,6-glucan. This glucan functions as a fundamental structural element within the fungal cell wall, covalently linking mannoproteins into the β-1,3-glucan-chitin network. Previously, a highly hydrolytically active β-1,6-glucanase, MoGlu16, was identified in Magnaporthe oryzae. However, its impacts on the pathogenicity of the blast fungus remain unexplored. In this study, to elucidate the detailed biological function of this protein, we generated the ΔMoglu16 mutant strain by knocking out the MoGLU16 gene encoding the β-1,6-glucanase via homologous recombination. Compared to the wild-type strain Guy11, ΔMoglu16 mutant exhibited a significantly slower vegetative growth rate, with a reduction of approximately 52% on MM medium. Its cell wall structure was altered, characterized by a 13.7% decrease in β-1,6-glucan content and a 12.2% increase in chitin. Furthermore, the mutant displayed increased sensitivity to cell wall-disturbing agents. In addition, the deletion of MoGLU16 exerted a minor influence on the early developmental stages of conidia, but severely compromised M. oryzae infection and pathogenicity. These findings suggested that MoGlu16 was essential for mycelial growth and pathogenicity of M. oryzae, thereby providing a crucial theoretical basis for the development of novel fungicides targeting β-1,6-glucan.