Abstract
Trichothecene toxins are confirmed or suspected virulence factors of various plant-pathogenic Fusarium species. Plants can detoxify these to a variable extent by glucosylation, a reaction catalyzed by UDP-glucosyltransferases (UGTs). Due to the unavailability of analytical standards for many trichothecene-glucoconjugates, information on such compounds is limited. Here, the previously identified deoxynivalenol-conjugating UGTs HvUGT13248 (barley), OsUGT79 (rice) and Bradi5g03300 (Brachypodium), were expressed in E. coli, affinity purified, and characterized towards their abilities to glucosylate the most relevant type A and B trichothecenes. HvUGT13248, which prefers nivalenol over deoxynivalenol, is also able to conjugate C-4 acetylated trichothecenes (e.g., T-2 toxin) to some degree while OsUGT79 and Bradi5g03300 are completely inactive with C-4 acetylated derivatives. The type A trichothecenes HT-2 toxin and T-2 triol are the kinetically preferred substrates in the case of HvUGT13248 and Bradi5g03300. We glucosylated several trichothecenes with OsUGT79 (HT-2 toxin, T-2 triol) and HvUGT13248 (T-2 toxin, neosolaniol, 4,15-diacetoxyscirpenol, fusarenon X) in the preparative scale. NMR analysis of the purified glucosides showed that exclusively β-d-glucosides were formed regio-selectively at position C-3-OH of the trichothecenes. These synthesized standards can be used to investigate the occurrence and toxicological properties of these modified mycotoxins.
Highlights
Recombinant OsUGT79 was previously identified as an efficient catalyst for DON-3-Glc and NIV-3-Glc synthesis
It is active with HT2 and T-2 triol (T2 triol), and could be applied to synthesize HT2-glucoside and T2 triol-glucoside
In this paper we report the synthesis, purification, and characterization of β-glucoside-standards of several trichothecene toxins
Summary
1. Introduction are a large group of toxic fungal secondary metabolites with a common tricyclic. They are produced by several fungal genera of the order. Trichothecenes are a large group of toxic fungal secondary metabolites with a common tricyclic. Hypocreales, and their primary mode of action is the inhibition of eukaryotic protein synthesis [1]. F. sporotrichioides, F. langsethiae, and F. poae are common producers of the fusarenon X, FUSX) are biosynthetic precursors of DON and NIV [1]. T2 and HT2 are among the most toxic and F. poae are common producers of the type A trichothecenes T-2 toxin (T2) and HT-2 toxin (HT2).
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