Transcriptome Analysis of the Barley–Deoxynivalenol Interaction: Evidence for a Role of Glutathione in Deoxynivalenol Detoxification

Abstract

Trichothecenes are a major group of toxins produced by phytopathogenic fungi, including Fusarium graminearum. Trichothecenes inhibit protein synthesis in eukaryotic cells and are toxicologically relevant mycotoxins for humans and animals. Because they promote plant disease, the role of host responses to trichothecene accumulation is considered to be an important aspect of plant defense and resistance to fungal infection. Our overall objective was to examine the barley response to application of the type B trichothecene deoxynivalenol (DON). We found that DON is diluted by movement from the application site to acropetal and basipetal florets. A susceptible barley genotype converted DON to DON-3-O-glucoside, indicating that UDP-glucosyltransferases capable of detoxifying DON must exist in barley. RNA profiling of DON-treated barley spikes revealed strong upregulation of gene transcripts encoding ABC transporters, UDP-glucosyltransferases, cytochrome P450s, and glutathione-S-transferases. We noted that transcripts encoding cysteine synthases were dramatically induced by DON, and that toxin-sensitive yeast on glutathione- or cysteine-supplemented media or carrying a gene that encodes a cysteine biosynthetic enzyme exhibit DON resistance, suggesting that preventing glutathione depletion by increasing cysteine supply could play a role in ameliorating the impact of DON. Evidence for nonenzymatic formation of DON-glutathione adducts in vitro was found using both liquid chromatography-mass spectrometry and nuclear magnetic resonance analysis, indicating that the formation of DON-glutathione conjugates in vivo may reduce the impact of trichothecenes. Our results indicate that barley exhibits multiple defense mechanisms against trichothecenes.

Scientific Opinion on the risks for human and animal health related to the presence of modified forms of certain mycotoxins in food and feed

“…Similar studies have also preliminarily addressed the formation of DON3G in barley and durum wheat (Gardiner et al, 2010;.…”

A Brachypodium UDP-Glycosyltransferase Confers Root Tolerance to Deoxynivalenol and Resistance to Fusarium Infection

“…4). Previous studies on wheat and barley have established that genes encoding UGTs are up-regulated following fungal infection (Lemmens et al, 2005;Boddu et al, 2007;Gottwald et al, 2012) or DON application (Gardiner et al, 2010;Lulin et al, 2010). However, in several transcriptomic studies, overall differences in gene expression were partly due to their different genetic backgrounds between FHBresistant and -susceptible lines rather than differences in specific resistance loci (Jia et al, 2009).…”

“…The induction of jasmonate-regulated allene oxide synthase and 12-oxo-phytodienoic acid reductase (Gottwald et al, 2012;Kugler et al, 2013;Xiao et al, 2013), and the related metabolites linoleic and linolenic acids, jasmonates, and traumatic acid (Bollina et al, 2011;Kumaraswamy et al, 2011a), have been described as markers of quantitative resistance to FHB. Other common features were associated with defense responses such as the induction of b-1,3-glucanases, chitinases, and thaumatin-like proteins, the scavenging of reactive oxygen species, and xenobiotic detoxification by family 1 UDP-glycosyltransferases, glutathione S-transferases, cytochrome P450-monooxygenases, and transporter detoxification (Boddu et al, 2006;Golkari et al, 2007;Jia et al, 2009;Gardiner et al, 2010;Foroud et al, 2012;Kugler et al, 2013;Xiao et al, 2013). Other phenomena that have been linked to resistance to FHB include increased photosynthesis and carbohydrate metabolism involving chloroplast oxygen-evolving enhancer proteins, NAD(P) + -binding proteins, and the pentose phosphate pathway (Kugler et al, 2013;Zhang et al, 2013).…”

Deoxynivalenol resistance as a component of FHB resistance

“…A subsequent transcriptome study of this barley cv. Morex confirmed that genes encoding ABC transporters, UGTs, CYP450s and GSTs were responsive to pure DON (Gardiner et al 2010) and that overexpression of cystathionine β-synthase, a key enzyme for glutathione production, enhanced the conversion of DON to the less toxic derivative DON-glutathione in yeast.…”