| Summary: | Ras proteins are monomeric G proteins that are ubiquitous in fungal cells and play important roles in fungal growth, virulence, and environmental responses. <i>Botrytis cinerea</i> is a phytopathogenic fungus that infects various crops. However, under specific environmental conditions, the overripe grapes infected by <i>B. cinerea</i> can be used to brew valuable noble rot wine. As a Ras protein, the role of Bcras2 in the environmental responses of <i>B. cinerea</i> is poorly understood. In this study, we deleted the <i>Bcras2</i> gene using homologous recombination and examined its functions. Downstream genes regulated by <i>Bcras2</i> were explored using RNA sequencing transcriptomics. It was found that Δ<i>Bcras2</i> deletion mutants showed significantly reduced growth rate, increased sclerotia production, decreased resistance to oxidative stress, and enhanced resistance to cell wall stress. Additionally, <i>Bcras2</i> 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 <i>Bcras2</i> positively regulates growth, oxidative stress resistance, and conidial melanin-related genes expression, and negatively regulates sclerotia production, cell wall stress resistance and sclerotial melanin-related genes expression. These results revealed previously unknown functions of <i>Bcras2</i> in environmental responses and melanin metabolism in <i>B. cinerea</i>.
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