Functional Characterization of Cytochromes P450 Linkedto Herbicide Detoxification and Selectivity in Winter Wheat and theProblem Competing Weed Blackgrass

The selective chemical control of wild grasses in wheat is primarily determined by the relative rates of herbicide metabolism, with the superfamily of cytochromes P450 (CYPs) playing a major role in catalyzing phase 1 detoxification reactions. This selectivity is enhanced by herbicide safeners, which induce CYP expression in cereals, or challenged by the evolution of nontarget site resistance (NTSR) in weeds such as blackgrass. Using transcriptomics, proteomics, and functional expression in recombinant yeast, CYPs linked to safener treatment and NTSR have been characterized in wheat and blackgrass. Safener treatment resulted in the induction of 13 families of CYPs in wheat and 5 in blackgrass, with CYP71, CYP72, CYP76, and CYP81 members active toward selective herbicides in the crop. Based on their expression and functional activities, three inducible <i>Ta</i>CYP81s were shown to have major roles in safening in wheat. In contrast, a single <i>Am</i>CYP81 that was enhanced by NTSR, but not by safening, was found to dominate herbicide detoxification in blackgrass.