Arabidopsis plants with defective hydrolysis of indole glucosinolates show increased resistance to the fungal pathogen Botrytis cinerea

Plants have evolved the ability to produce antimicrobial compounds to protect against pathogens and pests. In the Brassicaceae family, aliphatic and indole glucosinolates, derived from methionine and tryptophan, are stored in the vacuole. When tissues are damaged, myrosinases hydrolyze these glucosinolates into isothiocyanates, nitriles, and other antimicrobial compounds. In Arabidopsis, the PENETRATION2 (PEN2) myrosinase hydrolyzes indole glucosinolates, aiding in fungal pathogen defense. Surprisingly, pen2 loss-of-function mutants show strong resistance to the fungal necrotroph Botrytis cinerea, particularly to strains sensitive to the indole phytoalexin camalexin. Metabolite analysis reveals increased camalexin accumulation in pen2 leaves in response to B. cinerea. The resistance conferred by the pen2 mutation is lost in a cyp71a12cyp71a13 mutant background, which is defective in indole glucosinolate and camalexin biosynthesis, indicating that the reduced susceptibility of PEN2-lacking plants depends on increased camalexin production. These findings underscore the complex feedback mechanisms that control the accumulation of different antimicrobial compounds during infection.