Abstract
Glucosinolates are a diverse class of S- and N-containing secondary metabolites that play a variety of roles in plant defense. In this study, we used Arabidopsis thaliana mutants that contain different amounts of glucosinolates and glucosinolate-breakdown products to study the effects of these phytochemicals on phytopathogenic fungi. We compared the fungus Botrytis cinerea, which infects a variety of hosts, with the Brassicaceae-specific fungus Alternaria brassicicola. B. cinerea isolates showed variable composition-dependent sensitivity to glucosinolates and their hydrolysis products, while A. brassicicola was more strongly affected by aliphatic glucosinolates and isothiocyanates as decomposition products. We also found that B. cinerea stimulates the accumulation of glucosinolates to a greater extent than A. brassicicola. In our work with A. brassicicola, we found that the type of glucosinolate-breakdown product is more important than the type of glucosinolate from which that product was derived, as demonstrated by the sensitivity of the Ler background and the sensitivity gained in Col-0 plants expressing epithiospecifier protein both of which accumulate simple nitrile and epithionitriles, but not isothiocyanates. Furthermore, in vivo, hydrolysis products of indole glucosinolates were found to be involved in defense against B. cinerea, but not in the host response to A. brassicicola. We suggest that the Brassicaceae-specialist A. brassicicola has adapted to the presence of indolic glucosinolates and can cope with their hydrolysis products. In contrast, some isolates of the generalist B. cinerea are more sensitive to these phytochemicals.
Highlights
Glucosinolates are a diverse class of S- and N-containing secondary metabolites that are found mainly in members of the Brassicaceae [1]
Using A. thaliana mutants whose glucosinolate contents had been altered, we showed that B. cinerea displayed variable sensitivity to glucosinolates and their degradation products; whereas A. brassicicola was more tolerant of glucosinolates and their hydrolysis products
We demonstrated that the hydrolysis products of indolic glucosinolates are responsible for the differences observed between plant responses to B. cinerea and plant responses to A. brassicicola
Summary
Glucosinolates are a diverse class of S- and N-containing secondary metabolites that are found mainly in members of the Brassicaceae [1]. GSs Glucosinolates play a variety of roles in plant defense responses and cancer prevention. Significant progress has been made in understanding the biochemistry and genetics of glucosinolates biosynthesis [4,5] and how that biosynthesis is regulated over the course of plant development and in response to environmental cues [6,7]. They hydrolysis of glucosinolates is catalyzed by endogenous myrosinases (b-thioglucoside glucohydrolases) [8]. Myrosinase-associated proteins include the Arabidopsis thaliana epithiospecifier protein (ESP)
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