Submitted to: Journal of Biological Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/5/2007
Publication Date: 10/20/2007
Citation: Garvey, G.S., Mc Cormick, S.P., Rayment, I. 2007. Structural and functional characterization of the TRI101 trichothecene 3-O-acetyltransferase from Fusarium sporotrichioides and Fusarium graminearum: kinetic insights to combating Fusarium head blight. Journal of Biological Chemistry. 283:1660-1669. Interpretive Summary: Fusarium head blight is a disease of cereal crops that is caused by Fusarium species that produce trichothecene mycotoxins. It has serious economic and health impacts. Previous studies have shown that the trichothecenes are factors in the severity of the disease. One strategy that has been tried to combat the disease is to introduce a Fusarium sporotrichioides gene (Tri101) that protects that fungus from its own toxins into cereals such as wheat and barley. This gene essentially locks up the trichothecenes, converting them to less toxic products. We found that the Tri101 gene from Fusarium graminearum is 70 times better at locking up deoxynivalenol, the trichothecene toxin most commonly associated with U.S. outbreaks of wheat head blight. Wheat breeders and seed companies may be able to improve resistance to wheat head blight by inserting the F. graminearum gene into wheat.
Technical Abstract: Fusarium head blight (FHB) is a plant disease with serious economic and health impacts. It is caused by fungal species belonging to the genus Fusarium and the mycotoxins they produce. Although it has proved difficult to combat this disease, one strategy that has been examined is the introduction of an indigenous fungal protective gene into cereals such as wheat, barley, and rice. Thus far the gene of choice has been tri101, whose gene product catalyses the transfer of an acetyl group from acetyl Coenzyme A to the C3 hydroxyl moiety of several trichothecene mycotoxins. In vitro this has been shown to reduce the toxicity of the toxins by ~100 fold, but has demonstrated limited resistance to FHB in transgenic cereal. In order to understand the molecular basis for the differences between in vitro and in vivo resistance, the three-dimensional structures and kinetic properties of two TRI101 orthologs isolated from Fusarium sporotrichioides and Fusarium graminearum have been determined. The kinetic results reveal important differences in activity of these enzymes towards B-type trichothecenes such as deoxynivalenol. These differences in specificity can be explained in part by the three dimensional structures for the ternary complexes for both these enzymes with Coenzyme A and trichothecene mycotoxins. The structural and kinetic results together emphasize that the choice of an enzymatic resistance gene in transgenic crop protection strategies must take into account the kinetic profile of the selected protein.