Resistance to Fusarium Head Blight and Seedling Blight in Wheat Is Associated with Activation of a Cytochrome P450 Gene

One plant genotype displays a resistance phenotype at one development stage but a susceptible reaction to the same pathogen at another stage, which is referred to here as resistance inversion In wheat, Fusarium head blight (FHB)-resistant cv Sumat3 showed a Fusarium seedling blight (FSB)-susceptible reaction whereas FHB-susceptible cv Annong8455 exhibited FSB resistance when challenged with a Fusarium astaticum strain that produces deoxynivalenol (DON). The resistance to FHB and FSB in wheat was closely associated with expression of a plant cytochrome P450 gene in response to FHB pathogens and mycotoxins Quantitative real-time polymerase chain reaction analyses showed that expression of nine defense-related genes in spikes and seedlings was induced by the fungal infection, in which a massive accumulation of a plant cytochrome P450 gene, CYP709CI, was clearly associated with the resistance reaction in both seedling and spike The FHB-resistant Sumat3 accumulated 7-fold more P450 transcripts than did the FHB-susceptible Annong8455, while 84-fold more P450 transcripts were accumulated in the FSB-resistant Annong8455 than the FSB-susceptible Sumat3 A Fusarium strain with a disrupted Trt5 gene, which is not able to produce the first enzyme essential for trichothecene mycotoxin biosynthesis, also induced more P450 transcripts in FHB- and FSB-resistant cultivars The fungal activation of the P450 gene was more profound in the FSB-resistant reaction than the FHB-resistant reaction relative to then susceptible counterparts DON triggered a differential expression of the P450 gene with comparable patterns in spikes and seedlings in a resistance-dependent manner These results may provide a basis for dissecting mechanisms underlying FHB and FSB resistance reactions in wheat and revealing functions of the cytochrome P450 in plant detoxification and defense