UDP-Glucosyltransferases from Rice, Brachypodium, and Barley: Substrate Specificities and Synthesis of Type A and B Trichothecene-3-O-β-d-glucosides

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.

Enzymes for Detoxification of Various Mycotoxins: Origins and Mechanisms of Catalytic Action

“…Aflatoxin dialdehyde aldo-keto reductase AKR7A1 (Figure 2 [15,16], Table 1 [17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58]) was isolated from rat liver, and its structure in complex with NADP + was solved [59]. This enzyme is assumed to reduce both aldehyde groups of dialdehyde of hydroxy aflatoxin B 2a , forming from 8,9-dihydrodiol aflatoxin B 1 , resulted in dihydroxy derivative.…”

Relationship between genetic variability of flowering traits andFusariummycotoxin contamination in oats

“…Of more importance were differences in mycotoxin content between genotypes like Tim (low DON content) and Bessin (high DON content) or Keely (low DON content) and Scorpion (high DON content) with similar PH, AR, and BBCH in Panel 2. Possible reasons for such differences were detoxification of DON (Michlmayr et al, 2018) or a variation in trichome-type cells, which were found to be related to Fusarium ingress and resistance responses in barley (Imboden, Afton, & Trail, 2018).…”

Identification, Molecular Cloning, and Functional Characterization of a Wheat UDP-Glucosyltransferase Involved in Resistance to Fusarium Head Blight and to Mycotoxin Accumulation

“…The Bradi5g03300 UGT has recently been shown to be able to conjugate different mycotoxins belonging to trichothecenes, either type A or type B, in recombinant protein assays (Michlmayr et al, 2018). Future studies investigating whether this novel wheat UGT also exhibits a level of substrate flexibility will be of special interest, in particular to estimate its ability to be used as a source a resistance against a wider range of Fusarium sp.…”