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

<div><p>In this study, a total of nine different biotransformation products of the <i>Fusarium mycotoxin</i> 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) <i>Fhb1</i> and/or <i>Qfhs.ifa-5A</i>. All cultivars carrying QTL <i>Fhb1</i> 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 <i>Fhb1</i>. Moreover, all wheat lines harboring <i>Fhb1</i> showed significantly elevated D3G/DON abundance ratios.</p></div

Overview of nine different DON biotransformation products in DON treated wheat samples.

<p>* Annotation based LC-HRMS/MS spectra revealing characteristic fragment ions.</p><p>** Identification of compounds based on authentic standard with similar retention time and LC-HRMS/MS spectra (data not shown).</p><p>^ǂ Biotransformation products have also been putatively identified in a previous study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119656#pone.0119656.ref024" target="_blank">24</a>].</p><p>Initial annotation for all biotransformation products was performed based on the maximum mass deviation of ± 3 ppm and relative retention order (deviation retention time: ± 0.2 min) compared to the same biotransformation products annotated in the former study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119656#pone.0119656.ref024" target="_blank">24</a>].</p

EICs of DON and its corresponding biotransformation products.

<p>EICs of accurate mass traces (± 3 ppm) of DON and its corresponding biotransformation products in a wheat sample harvested 96 hours post treatment with 1 mg DON. Due to low abundance, EIC intensities of DON-di-hexoside were multiplied by a factor of 10.</p

Overview on DON degradation.

<p>Time course for the degradation of DON (1 mg) of wheat lines ‘CM-82036’, C1, C2, C3, C4 and ‘Remus’. Wheat ears were sampled 0, 12, 24, 48, and 96 hours after treatment (n = 5 biological replicates per time point and wheat line). a) Degradation rate of DON. b) boxplot of relative concentrations 96 h after DON treatment. c) DON-glucoside/DON ratio 96 h after DON treatment. * Significantly differing DON levels between wheat lines with and without resistance QTL <i>Fhb1</i> based on a non-paired t-test (5% global significance threshold).</p

Detoxification of DON via glucosylation/sugar alcohol.

<p>Glucose/sugar alcohol related detoxification of DON. Relative formation rates for the biotransformation products DON-glucoside (a), DON-malonyl-glucoside (b), 15-acetyl-DON-3-glucoside (c) and DON-hexitol (d). Additionally, for each biotransformation product boxplots for relative metabolite abundance observed 96 h after DON treatment were generated. * Significantly differing biotransformation product levels between wheat lines with and without resistance QTL <i>Fhb1</i> based on a non-paired t-test (5% global significance threshold).</p