Autophagy-Related Gene 4 Participates in the Asexual Development, Stress Response and Virulence of Filamentous Insect Pathogenic Fungus Beauveria bassiana .

Autophagy is a conserved mechanism for the turnover of intracellular components. Among the 'core' autophagy-related genes (), the cysteine protease Atg4 plays an important role in the activation of Atg8 by exposing the glycine residue at its extreme carboxyl terminus. In the insect fungal pathogen , a yeast ortholog of Atg4 was identified and functionally analyzed. Ablation of the gene blocks the autophagic process during fungal growth under aerial and submerged conditions. Gene loss did not affect fungal radial growth on various nutrients, but Δ exhibited an impaired ability to accumulate biomass. The mutant displayed increased sensitivity to stress caused by menadione and hydrogen peroxide. Δ generated abnormal conidiophores with reduced production of conidia. Additionally, fungal dimorphism was significantly attenuated in gene disruption mutants. Disruption of resulted in significantly weakened virulence in topical and intrahemocoel injection assays. Our study indicates that BbAtg4 contributes to the lifecycle of via its autophagic roles.