Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/14/2004
Publication Date: 4/14/2004
Citation: Mc Cormick, S.P., Harris, L.J., Alexander, N.J., Ouellet, T., Saparno, A., Allard, S., Desjardins, A.E. 2004. Tri1 in fusarium graminearum encodes a p450 oxygenase. Applied And Environmental Microbiology. 70(4):2044-2051. Interpretive Summary: Trichothecenes are toxic substances produced by the wheat disease fungus Gibberella zeae. We are interested in reducing or eliminating these toxins from wheat. In an effort to accomplish that goal, we are interested in understanding the biology of the fungus with regard to trichothecene production. We know that a group of genes are involved in the production of the trichothecene deoxynivalenol (DON) and in this report we concentrate on the function of one of those genes and its role in DON production. One way in which we study the functions of genes is to eliminate or knockout the gene of interest. We have knocked out one of the genes for DON production and describe the effects of this knockout on DON production. This has allowed us to learn more about the production of DON. A better understanding of the genes involved in DON production may lead to novel strategies for reducing or eliminating these toxins from wheat.
Technical Abstract: Gibberella zeae (asexual state Fusarium graminearum) is a major causal agent of wheat head blight and maize ear rot in North America and contaminates grain with deoxynivalenol and related trichothecene mycotoxins. To identify additional trichothecene biosynthetic genes, cDNA libraries were prepared from fungal cultures under trichothecene-inducing conditions in culture and in planta. A gene designated Fg1A2287 that was highly expressed under these conditions exhibited sequence similarity to cytochrome P450 monooxygenases, but only moderate similarity to known trichothecene biosynthetic cytochrome P450s. To determine the function of Fg1A2287, gene disruptants were produced and assessed for trichothecene production. Gene disruptants no longer produced 15-acetyldeoxynivalenol, which is oxygenated at carbons 7 (C-7) and C-8, but rather accumulated calonectrin and 3-deacetylcalonectrin, which are not oxygenated at either C-7 or C-8. These results indicate that gene Fg1A2287 encodes a cytochrome P450 responsible for oxygenation at one or both of these position. Despite the relatively low level of DNA and amino acid sequence similarity between the two genes, Fg1A2287 from G. zeae is a probable homologue of Tri1, which encodes a cytochrome P450 required for C-8 oxygenation in F. sporotrichioides.