Functional Characterization of Cytochromes P450 Linked to Herbicide Detoxification and Selectivity in Winter Wheat and the Problem 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 TaCYP81s were shown to have major
roles in safening in wheat. In contrast, a single AmCYP81 that was enhanced by NTSR, but not by safening, was found to
dominate herbicide detoxification in blackgrass.