Poster # 124

Gerit Bethke¹, Yadong Huang¹, Goetz Hensel², Shane Heinen¹, Chaochih Liu ¹, Skylar Wyant¹, Xin Li¹, Susan McCormick³, Peter Morrell¹, Yanhong Dong⁴, Jochen Kumlehn², Silvio Salvi⁵, Franz Berthiller⁶, and Gary J. Muehlbauer¹
1. University of Minnesota, Department of Agronomy and Plant Genetics, Saint Paul, MN, USA
2. Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Plant Reproductive Biology, Gatersleben, Germany
3. USDA-ARS NCAUR, Mycotoxin Prevention and Applied Microbiology Research, Peoria IL, USA
4. University of Minnesota, Department of Plant Pathology, Saint Paul, MN, USA
5. University of Bologna, Department of Agricultural and Food Sciences, Bologna, Italy
6. University of Natural Resources and Life Sciences, Vienna (BOKU), Department of Agrobiotechnology, Tulln, Austria
Corresponding Author: Gary J. Muehlbauer, muehl003@umn.edu

Gerit Bethke

Fusarium head blight (FHB) of Hordeum vulgare (barley) causes reduction in yield and grain quality. Glycosylation of the trichothecene mycotxin deoxynivalenol (DON) to the less toxic DON-3-glucoside (D3G) is catalyzed by UDP-glucosyl transferases (UGTs). Barley UGT13248, was previously shown to convert DON to D3G in yeast, Arabidopsis and wheat. In wheat, expression of UGT13248 decreased FHB severity. To explore the natural genetic diversity of UGT13248 in barley, we sequenced UGT13248 from 26 barley accessions with varying degree of FHB resistance and analyzed the UGT13248 sequence of 20 accessions of the barley pan genome. We identified five protein variants. A survey of the UGT13248 sequence from exome capture sequencing data of a diverse panel of barley genotypes identified eight additional protein variants. Accessions carrying eleven of these thirteen UGT13248 protein variants did not show strongly reduced sensitivity to DON in seedling root growth assays, suggesting that UGT13248 is functionally conserved.

Barley lines overexpressing UGT13248 were generated and two independent TILLING lines carrying mutations in UGT13248 were identified. Protein models suggested that these mutations were in close proximity to the UDP-sugar binding site, UGT13248 (T368I) and UGT13248 (H369Y). The T368I and H369Y mutants showed hypersensitivity to DON in seedling root growth assays and strongly impaired conjugation of DON to D3G in barley spikes. Constitutive expression of UGT13248 resulted in increased resistance to DON in seedling root growth assays and increased conjugation of DON to D3G in spikes. Field tests of the TILLING mutants showed increased FHB disease severity, suggesting that DON to D3G conversion contributed to FHB resistance. Point inoculation experiments showed increased FHB disease severity and increased spread of FHB symptoms in the spikes of the TILLING mutants as well as reduced disease severity in plants overexpressing UGT13248. The rachis of the H369Y mutant contained more Fusarium graminearum and DON compared to wild-type plants. F. graminearum was detected within rachis nodes up to four nodes basi- and acropetal of the inoculated spikelet in H369Y mutants but not in wild-type plants. We conclude that UGT13248 is required for Type 2 resistance in barley.

This material is based upon work supported by the U.S. Department of Agriculture, under Agreement No. 59-0206-4-021. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.