Ras2 is responsible for the environmental responses, melanin metabolism, and virulence of Botrytis cinerea
Ras proteins are monomeric G proteins that are ubiquitous in fungal cells and play important roles in the growth, development, virulence and environmental responses of fungi. Botrytis cinerea is a notorious phytopathogenic fungi infecting various cash crops. However, under specific environmental conditions, the overripe grapes infected by B. cinerea can be used to brew valuable noble rot wine. As a Ras protein, the role of Ras2 in the environmental responses of B. cinerea is poorly understood. In this study, we deleted the B. cinerea Ras2 protein by homologous recombination and examined its functions in growth, development, virulence and environmental responses. Meanwhile, the downstream genes regulated by Ras2 were explored through RNA sequencing transcriptomics. It was found that Bcras2 deletion mutants showed significantly reduced growth rate, increased sclerotia production, and enhanced resistance to oxidative and cell wall stresses. In addition, Ras2 deletion promoted the expression of melanin-related genes in sclerotia and decreased the expression of melanin-related genes in conidia. The above results indicate that Ras2 positively regulates the growth and conidial melanin-related genes expression, and negatively regulates sclerotia production, sclerotial melanin-related genes expression, and the resistance to oxidative/cell wall stresses of B. cinerea.