A barley UDP-glucosyltransferase inactivates nivalenol and provides Fusarium Head Blight resistance in transgenic wheat

Abstract

Fusarium Head Blight is a disease of cereal crops that causes severe yield losses and mycotoxin contamination of grain. The main causal pathogen, Fusarium graminearum, produces the trichothecene toxins deoxynivalenol or nivalenol as virulence factors. Nivalenol-producing isolates are most prevalent in Asia but co-exist with deoxynivalenol producers in lower frequency in North America and Europe. Previous studies identified a barley UDP-glucosyltransferase, HvUGT13248, that efficiently detoxifies deoxynivalenol, and when expressed in transgenic wheat results in high levels of type II resistance against deoxynivalenol-producing F. graminearum. Here we show that HvUGT13248 is also capable of converting nivalenol into the non-toxic nivalenol-3-O-β-d-glucoside. We describe the enzymatic preparation of a nivalenol-glucoside standard and its use in development of an analytical method to detect the nivalenol-glucoside conjugate. Recombinant Escherichia coli expressing HvUGT13248 glycosylates nivalenol more efficiently than deoxynivalenol. Overexpression in yeast, Arabidopsis thaliana, and wheat leads to increased nivalenol resistance. Increased ability to convert nivalenol to nivalenol-glucoside was observed in transgenic wheat, which also exhibits type II resistance to a nivalenol-producing F. graminearum strain. Our results demonstrate the HvUGT13248 can act to detoxify deoxynivalenol and nivalenol and provide resistance to deoxynivalenol- and nivalenol-producing Fusarium.

Keywords: Fusarium Head Blight; Fusarium graminearum; UDP-glycosyltransferase; nivalenol; trichothecene; wheat..

Fig. 1.

Growth of glycosyltransferase-expressing yeast on rich medium containing the indicated concentrations of DON and NIV.

Fig. 2.

NIV-3-glucoside is less toxic than NIV and DON on wheat ribosomes.

Fig. 3.

Root growth of transgenic Arabidopsis thaliana expressing HvUGT13248 in the Col-0 background on half-strength MS medium containing (A) 0 mg l^–1 NIV, (B) 20 mg l^–1 NIV, (C) 40 mg l^–1 NIV, and (D) 100 mg l^–1 NIV.

Fig. 4.

FHB severity of transgenic wheat expressing HvUGT13248 at 21 d after point inoculation with NIV-producing F. graminearum strain #02-15 in three greenhouse trials. Lines #8, #15, #19, and #37 were transgenic wheat expressing HvUGT13248, and ‘Bobwhite’ was the non-transformed control. ‘Wheaton’ was the susceptible check and ‘Sumai 3’ was the resistant check.

Fig. 5.

HvUGT13248 promotes NIV to NIV3G conjugation in transgenic wheat. (A) NIV and NIV3G concentrations in ‘Bobwhite’ (BW) and transgenic line #19 at 0, 2, 6, 12, 24, 36, 48, 72, 96, and 336 h after NIV treatment. ‘BW-NIV’ and ‘UGT-NIV’ are the NIV content in BW or transgenic event #19 at each time point, respectively. ‘BW-NIV3G’ and ‘UGT-NIV3G’ are the NIV3G content in BW or transgenic line #19 at each time point, respectively. (B) Fold change of the molar ratio of NIV3G to NIV concentrations in BW and transgenic line #19 at each time point.