Biotransformation of the Mycotoxin Deoxynivalenol in Fusarium Resistant and Susceptible Near Isogenic Wheat Lines

Abstract

In this study, a total of nine different biotransformation products of the Fusarium mycotoxin deoxynivalenol (DON) formed in wheat during detoxification of the toxin are characterized by liquid chromatography—high resolution mass spectrometry (LC-HRMS). The detected metabolites suggest that DON is conjugated to endogenous metabolites via two major metabolism routes, namely 1) glucosylation (DON-3-glucoside, DON-di-hexoside, 15-acetyl-DON-3-glucoside, DON-malonylglucoside) and 2) glutathione conjugation (DON-S-glutathione, “DON-2H”-S-glutathione, DON-S-cysteinyl-glycine and DON-S-cysteine). Furthermore, conjugation of DON to a putative sugar alcohol (hexitol) was found. A molar mass balance for the cultivar ‘Remus’ treated with 1 mg DON revealed that under the test conditions approximately 15% of the added DON were transformed into DON-3-glucoside and another 19% were transformed to the remaining eight biotransformation products or irreversibly bound to the plant matrix. Additionally, metabolite abundance was monitored as a function of time for each DON derivative and was established for six DON treated wheat lines (1 mg/ear) differing in resistance quantitative trait loci (QTL) Fhb1 and/or Qfhs.ifa-5A. All cultivars carrying QTL Fhb1 showed similar metabolism kinetics: Formation of DON-Glc was faster, while DON-GSH production was less efficient compared to cultivars which lacked the resistance QTL Fhb1. Moreover, all wheat lines harboring Fhb1 showed significantly elevated D3G/DON abundance ratios.

Advanced LC–MS-based methods to study the co-occurrence and metabolization of multiple mycotoxins in cereals and cereal-based food

“…Recently, metabolomics-based approaches have found their place in the mycotoxin research field to (1) study the metabolism of mycotoxins in grains, especially in resistant plant varieties such as Fusarium-resistant wheat [85], (2) explore the co-occurrence of these secondary fungal metabolites with plant metabolites, and (3) reveal the formation of so far unknown metabolites that can also be present in cereal-based food. In line with this, two different strategies can be distinguished: targeted and untargeted metabolomics.…”

Preparation and Characterization of Cysteine Adducts of Deoxynivalenol

“…7 Kluger et al 8 reported formation of DON−glutathione (DON−GSH), as well as the presence of the degradation products DON−cysteinylglycine and DON−cysteine (DON− Cys) in DON-treated wheat lines. 8 The glutathione pathway is one of the most common types of xenobiotic modifications during phase II metabolism, where the conjugation reaction occurs between the thiol group of the amino acid cysteine in GSH and an electrophilic feature in xenobiotic. 9 Studies with model thiols showed that thiol addition to DON can follow two reaction mechanisms: reversible Michael addition to C-10 of the α,β-unsaturated ketone, and irreversible addition to C-13 of the epoxide ring.…”

“…10 These adducts were shown to exist as equilibrium mixtures of the hemiketal and ketone forms of the DON−thiol model compounds. 11,10 The reported DON− GSH, DON−Cys, and DON−CysGly conjugates 8 have so far only been tentatively identified by LC−HRMS/MS, and their exact chemical structures are yet to be determined. DON−Cys is expected to be one of the major breakdown products of DON−GSH in vivo.…”

Behaviour of durum wheat cultivars towards deoxynivalenol content: A multi-year assay in Italy

“…Resistance aspects determine the severity of FHB (I-IV resistance), however, other mechanisms may influence DON content in kernels, which limit the trichothecene accumulation in cereals, including the transformation of the mycotoxin that is named type V-1 (Boutigny et al, 2008). Several studies are available in literature about the mechanisms of resistance to DON which comprise the conversion of DON into less toxic metabolites, such as deoxynivalenol-3-O-glucoside (D3G), with a good correlation between FHB resistance and DON conversion rate, expressed as [D3G]/[DON] ratio in durum wheat (Audenaert et al, 2013;Berthiller et al, 2005;Cirlini et al, 2014;Kluger et al, 2015;Lemmens et al, 2005) and DON-glutathione (DON-GSH) (Krska 619 188 130 152 35 30 28 81 Claudio 846 338 102 106 23 26 24 38 Duilio 992 341 178 134 25 41 20 44 Iride 658 239 135 126 22 33 21 44 Saragolla 564 167 92 113 30 53 40 47 Simeto 1464 428 211 222 19 34 27 50 Svevo 583 70 78 111 <LOD 26 30 35 LOD, limit of detection (18.5 μg/kg). Results less than the limit of detection were set to 9.25 for the calculation of means.…”