Glc8, a regulator of protein phosphatase type 1, mediates oxidation tolerance, asexual development and virulence in Beauveria bassiana, a filamentous entomopathogenic fungus

Protein phosphatase type 1 (PP1) plays an important role in cellular metabolism and development in yeast. In PP1 enzyme complex, Glc8 protein is a global regulatory subunit and regulates many physiological processes. However, its biological roles are unexplored in filamentous fungi. In this study, we characterized a yeast ortholog of Glc8 in Beauveria bassiana, a filamentous entomopathogenic fungus. Gene disruption of BbGlc8 had no significant effect on vegetative growth, but resulted in a significant reduction in conidiation (51%) and blastospore yield (55%) in the mutant. The ΔBbGlc8 mutant displayed an enhanced sensitivity to oxidative stress and a weakened virulence as indicated by cuticle infection and intrahemocoel injection assays. Transcriptomic analysis indicated that the genes regulated by BbGlc8 during conidiation were primarily associated with metabolism, cell rescue and cell wall formation. Notably, as a down-regulated gene in ΔBbGlc8 mutant, BbOsmC2 (a member of OsmC protein family) contributes to fungal resistance to salt stress, spore differentiation and virulence. Thus, BbOsmC2 functions as a down-stream target of BbGlc8 during spore differentiation, but not in stress response. Our findings indicate that BbGlc8 contributes to the biocontrol potential of B. bassiana by mediating comprehensive genetic pathways.