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Trichothecene diversity and role of plant detoxification enzymes in host resistance

Gerhard Adam: University of Natural Resources and Life Sciences, Vienna

<div>Trichothecenes produced by phytopathogenic fungi are a major agricultural problem. These mycotoxins act as inhibitors of eukaryotic protein synthesis and play a role as fungal virulence factors. The ability of plants to counteract toxicity is difficult to study, since detoxification is typically mediated by members of large gene families. Individual members of the gene family 1 of UDP-glycosyltransferases (UGT, comprising about 160-180 genes in diploid plants) are able to convert deoxynivalenol (DON) and other trichothecenes into the respective glucosides. Transgenic wheat or <em>Brachypodium</em> overexpressing such UGT genes showed increased <em>Fusarium</em> resistance. Recombinant UGTs revealed large differences in affinity for different substrates. Structural changes allowing to (at least partially) escape detoxification seem to be a driving force in the structural diversification of trichothecenes. For instance, loss of <em>TRI13</em> function causes a switch from nivalenol (NIV) to DON production in <em>F. graminearum</em>. Barley UGT13248 showed lower affinity for DON than NIV indicating this may be advantageous. Yet, the frequently clustered UGTs can evolve new specificity. For instance, while UGT Bradi5g02780 can only detoxify NIV efficiently, the highly similar Bradi5g03300 has higher affinity for DON. Glutathione-mediated detoxification is another trichothecene resistance mechanism, recent progress in the study of the large GST family (glutathione-S-transferases) will be presented.</div>