Abstract:
Brassicales plants produce glucosinolates and myrosinases that generate toxic isothiocyanates
conferring broad resistance against pathogens and herbivorous insects.
Nevertheless, some cosmopolitan fungal pathogens, such as the necrotrophic white mold
Sclerotinia sclerotiorum, are able to infect many plant hosts including glucosinolate producers.
Here, we show that S. sclerotiorum infection activates the glucosinolate-myrosinase system,
and isothiocyanates contribute to resistance against this fungus. S. sclerotiorum metabolizes
isothiocyanates via two independent pathways: conjugation to glutathione and, more effectively,
hydrolysis to amines. The latter pathway features an isothiocyanate hydrolase that is
homologous to a previously characterized bacterial enzyme, and converts isothiocyanate into
products that are not toxic to the fungus. The isothiocyanate hydrolase promotes fungal
growth in the presence of the toxins, and contributes to the virulence of S. sclerotiorum on
glucosinolate-producing plants.
