Poster # 113

Gerit Bethke¹, Yadong Huang¹, Goetz Hensel², Skylar Wyant¹, Xin Li¹ , Shane Heinen¹, Susan McCormick³, Peter Morrell¹, Yanhong Dong⁴, Jochen Kumlehn², Silvio Salvi⁵, Franz Berthiller⁶, 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

Gary Muehlbauer

University of Minnesota

Fusarium head blight (FHB) of Hordeum vulgare (barley) can cause significant reduction in yield and grain quality by contamination with trichothecene mycotoxins including deoxynivalenol (DON). Glycosylation of DON to the less toxic DON-3-glucoside (D3G) is thought to be 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 28 barley accessions with varying degree of FHB resistance and identified six protein variants. A survey of the UGT13248 sequence from exome capture sequencing data of 34 elite barley lines, 182 wild barley accessions and 317 barley landraces identified seven non-synonymous changes. Accessions carrying any of these UGT13248 protein variants did not show altered sensitivity to DON on seedling root growth assays. These results suggest that mutations in UGT13248 are rare and that UGT13248 is highly conserved.

We next generated barley lines overexpressing UGT13248 and identified two independent TILLING lines carrying mutations in UGT13248 in close proximity to the UDP-sugar binding site, UGT13248 (T368I) and UGT13248 (H369Y). The UGT13248 (T368I) and (H369Y) mutants showed hypersensitivity to DON root growth inhibition in seedlings and strongly impaired conjugation of DON to D3G in barley spikes. Constitutively expressing HvUGT13248 in a susceptible barley cultivar provided resistance to DON root growth inhibition and increased conjugation of DON to D3G in spikes. Field tests of TILLING mutants showed increased FHB disease severity, suggesting that DON to D3G conversion contributes to FHB resistance. Point inoculation experiments showed increased FHB disease severity and increased spread of FHB symptoms in the spikes of TILLING mutants as well as reduced disease severity in plants overexpressing UGT13248. The rachis of the UGT13248 (H369Y) mutant contained more F. graminearum and DON compared to wild-type plants. Further, spread of F. graminearum was detected in rachis nodes adjacent to inoculated spikelets of UGT13248 (H369Y) plants but not in wild-type plants. Taken together, our data suggest that UGT13248 is required for Type 2 resistance in barley.

ACKNOWLEDGEMENT AND DISCLAIMER

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.