The Autophagy Gene BcATG8 Regulates the Vegetative Differentiation and Pathogenicity of Botrytis cinerea

Autophagy is a conserved degradation process that maintains intracellular homeostasis to ensure normal cell differentiation and development in eukaryotes. ATG8 is one of the key molecular components of the autophagy pathway. In this study, we identified and characterized BcATG8, a homologue of Saccharomyces cerevisiae (yeast) ATG8 in the necrotrophic plant pathogen Botrytis cinerea Yeast complementation experiments demonstrated that BcATG8 can functionally complement the defects of the yeast ATG8 null mutant. Direct physical interaction between BcAtg8 and BcAtg4 was detected in the yeast two-hybrid system. Subcellular localization assays showed that green fluorescent protein-tagged BcAtg8 (GFP-BcAtg8) localized in the cytoplasm as preautophagosomal structures (PAS) under general conditions but mainly accumulated in the lumen of vacuoles in the case of autophagy induction. Deletion of BcATG8 (ΔBcAtg8 mutant) blocked autophagy and significantly impaired mycelial growth, conidiation, sclerotial formation, and virulence. In addition, the conidia of the ΔBcAtg8 mutant contained fewer lipid droplets (LDs), and quantitative real-time PCR (qRT-PCR) assays revealed that the basal expression levels of the LD metabolism-related genes in the mutant were significantly different from those in the wild-type (WT) strain. All of these phenotypic defects were restored by gene complementation. These results indicate that BcATG8 is essential for autophagy to regulate fungal development, pathogenesis, and lipid metabolism in B. cinereaIMPORTANCE The gray mold fungus Botrytis cinerea is an economically important plant pathogen with a broad host range. Although there are fungicides for its control, many classes of fungicides have failed due to its genetic plasticity. Exploring the fundamental biology of B. cinerea can provide the theoretical basis for sustainable and long-term disease management. Autophagy is an intracellular process for degradation and recycling of cytosolic materials in eukaryotes and is now known to be vital for fungal life. Here, we report studies of the biological role of the autophagy gene BcATG8 in B. cinerea The results suggest that autophagy plays a crucial role in vegetative differentiation and virulence of B. cinerea.