title: NSP-Dependent Simple Nitrile Formation Dominates upon Breakdown of Major Aliphatic Glucosinolates in Roots, Seeds, and Seedlings ofArabidopsis thalianaColumbia-0.
abstract: One of the best-studied plant defense systems, the glucosinolate-myrosinase system of the Brassicales, is composed of thioglucosides known as glucosinolates and their hydrolytic enzymes, the myrosinases. Tissue disruption brings these components together, and bioactive products are formed as a consequence of myrosinase-catalyzed glucosinolate hydrolysis. Among these products, isothiocyanates have attracted most interest as chemical plant defenses against herbivores and pathogens and health-promoting compounds in the human diet. Previous research has identified specifier proteins whose presence results in the formation of alternative product types, e.g., nitriles, at the expense of isothiocyanates. The biological roles of specifier proteins and alternative breakdown products are poorly understood. Here, we assessed glucosinolate breakdown product profiles obtained upon maceration of roots, seedlings and seeds ofArabidopsis thalianaColumbia-0. We identified simple nitriles as the predominant breakdown products of the major endogenous aliphatic glucosinolates in root, seed, and seedling homogenates. In agreement with this finding, genes encoding nitrile-specifier proteins (NSPs) are expressed in roots, seeds, and seedlings. Analysis of glucosinolate breakdown in mutants with T-DNA insertions in any of the fiveNSPgenes demonstrated, that simple nitrile formation upon tissue disruption depended almost entirely onNSP2in seeds and mainly onNSP1in seedlings. In roots, about 70-80% of the nitrile-forming activity was due toNSP1andNSP3. Thus, glucosinolate breakdown product profiles are organ-specifically regulated inA. thalianaCol-0, and high proportions of simple nitriles are formed in some parts of the plant. This should be considered in future studies on biological roles of the glucosinolate-myrosinase system.
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig Braunschweig, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Wittstock
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig Braunschweig, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Meier
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig Braunschweig, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Dörr
authors.affiliation: Institute of Pharmaceutical Biology, Technische Universität Braunschweig Braunschweig, Germany.
authors.forename: Beena M
authors.initials: BM
authors.lastname: Ravindran
keywords: glucosinolate breakdown; myrosinase; nitrile-specifier protein; organ-specificity; simple nitrile