Abstract
The mycotoxin deoxynivalenol (DON) serves as a plant disease virulence factor for the fungi Fusarium graminearum and F. culmorum during the development of Fusarium head blight (FHB) disease on wheat. A wheat cytochrome P450 gene from the subfamily CYP72A, TaCYP72A, was cloned from wheat cultivar CM82036. TaCYP72A was located on chromosome 3A with homeologs present on 3B and 3D of the wheat genome. Using gene expression studies, we showed that TaCYP72A variants were activated in wheat spikelets as an early response to F. graminearum, and this activation was in response to the mycotoxic Fusarium virulence factor deoxynivalenol (DON). Virus induced gene silencing (VIGS) studies in wheat heads revealed that this gene family contributes to DON resistance. VIGS resulted in more DON-induced discoloration of spikelets, as compared to mock VIGS treatment. In addition to positively affecting DON resistance, TaCYP72A also had a positive effect on grain number. VIGS of TaCYP72A genes reduced grain number by more than 59%. Thus, we provide evidence that TaCYP72A contributes to host resistance to DON and conclude that this gene family warrants further assessment as positive contributors to both biotic stress resistance and grain development in wheat.
Highlights
Cytochrome P450s are heme-containing membrane-bound enzymes that can perform several types of oxidation-reduction reactions [1]
Based on the results of this study, we describe the first wheat cytochrome P450 variants to positively contribute to both DON resistance and grain development
Previous studies within our laboratory identified a novel cytochrome wheat transcript that was responsive to the Fusarium mycotoxin DON [4,5]
Summary
Cytochrome P450s are heme-containing membrane-bound enzymes that can perform several types of oxidation-reduction reactions [1]. They are involved in plant defence, secondary metabolite biosynthesis in the classical xenobiotic detoxification pathway [2,3]. There is compounding evidence to show that cytochrome P450s play a role in the host response to diseases, including the wheat response to Fusarium head blight (FHB) disease [4,5]. Fusarium graminearum (teleomorph: Gibberella zeae) is the principal causal agent of the disease. It infects wheat heads during flowering and thereby interferes with seed development leading to severe yield loss and reduced grain quality [7,8]. F. graminearum produces trichothecene mycotoxins in infected grains, predominantly deoxynivalenol (DON), which are harmful to plant, human and animal health [9,10,11]
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