DEVELOPING TRANSGENIC WHEAT AND BARLEY THAT EXHIBIT RESISTANCE TO FUSARIUM GRAMINEARUM VIA GLUCOSIDE CONJUGATION OF TRICHOTHECENE MYCOTOXINS

摘要

Fusarium graminearum infection of wheat and barley results in production of trichothecene mycotoxins including deoxynivalenol (DON) and nivalenol (NIV). These mycotoxins result in increased fungal virulence and reduce grain quality. Numerous transcriptomic studies have been conducted by our lab on the wheat/barley - F. graminearum interaction. These studies have identified a set of genes that may provide resistance to F. graminearum infection via conjugation, degradation or transport of trichothecenes. In addition, these studies also provide an understanding of F. graminearum genes that are expressed during infection. For example, the F. graminearum transcriptome responds differently to wheat carrying either resistant or susceptible alleles for Fhb1. From these studies we identified a barley UDP-glucosyltransferase (UGT13248) that exhibited DON resistance in yeast. Transgenic wheat expressing UGT13248 exhibited a high level of type II resistance in the greenhouse and resistance in the field that approaches the level of resistance conferred by Sumai 3. The mechanism of resistance conferred by UGT13248 is via conjugation of DON to DON-3-O-glucoside. Backcross families carrying Fhbl (type II resistance) derived from Rollag and the UGT13248 transgenewere screened in the greenhouse and field. The level of resistance in plants carrying Fhbl alone and those carrying Fhbl and the UGT13248 transgene were similar with a few FhbllUGT13248 containing lines exhibiting a slight reduction in severity comparedto those carrying Fhbl alone. The lack of reduction in disease severity may be due to either (1) Fhbl and the UGT13248 acting in the same manner or (2) the level of resistance conferred by Fhbl is so high that if is difficult to obtain increased resistance. It is noteworthy that transgenic wheat carrying UGT13248 also exhibits type II resistance to 3-ADON- and NIV-producing strains of F. graminearum, indicating that UGT13248 acts on a wide range of trichothecene mycotoxins. Interestingly, overexpression of UGT13248 in barley resulted in resistance to DON in root assays. Overall, our results demonstrate that UGT13248 is an effective gene for conferring resistance to F. graminearum infection.