A novel Major Facilitator Superfamily (MFS) transporter from Botrytis cinerea provides tolerance towards glucosinolate breakdown products and required for pathogenicity

Glucosinolates are a diverse class of secondary metabolites found mainly in members of the Brassicaceae (Cruciferae) and a few other unrelated families of dicotyledonous angiosperms. The importance of these metabolites has increased in the last few decades, upon discovery of their potential function in crop defense, agricultural biofumigation and cancer prevention. Upon plant injury or pathogen attack, glucosinolates are rapidly released and hydrolyzed to a multitude of physiologically active products so-called isothiocyanates. They have been described as promising molecules with antimicrobial activities against plant pathogens such as the causative agent of grey mold, Botrytis cinerea, this is a necrotrophic plant pathogen, which causes devastating losses on a number of crops. In the present study we studied the mechanisms of tolerance to glucosinolates in the fungus B. cinerea. Exposure of B. cinerea to glucosinolate breakdown products induces expression of the BcMFSI transporter that functions in the efflux of fungitoxic compounds. B. cinerea inoculated on wild-type A. thaliana plants activate the BcMFSI transporter to higher levels than on glucosinolate-deficient A. thaliana mutants. B. cinerea strains lacking functional BcMFSI are more sensitive to glucosinolate breakdown products in vitro and less virulent on plants. We demonstrate that a BcMFSI transporter is a virulence factor that increases tolerance of the pathogen towards glucosinolates. We also demonstrate that the BcMFSI gene can provide the yeast Saccharomyces cerevisiae tolerance towards glucosinolate hydrolysis products.