The small GTPase BcSec4 is involved in conidiophore development, membrane integrity, and autophagy in Botrytis cinerea

Small GTPases of the Rab family play important roles in membrane trafficking and autophagy. Previous studies have shown that the small GTPase Sec4 is involved in vegetative growth, protein secretion, and pathogenicity of fungal phytopathogens. In this study, the Rab GTPase BcSec4, an ortholog of the yeast Sec4p protein, was characterized in Botrytis cinerea . The ΔBcSEC4 mutant produces many abnormal conidiophores; it is thus defective in conidiation and displays attenuated pathogenicity. Notably, the germination and penetration of conidia are unaffected in the ΔBcSEC4 mutant. Further studies showed that the secretion of extracellular proteins was altered in the ΔBcSEC4 mutant, and the mutant showed impaired autophagy and defects in membrane integrity. Taken together, these results suggest that BcSec4 is critical for conidiophore development, membrane integrity, pathogenicity, and autophagy.