The P450 Gene CYP749A16 Is Required for Tolerance to the Sulfonylurea Herbicide Envoke in Cotton

Weed management is critical to global crop production and is complicated by rapidly evolving herbicide resistance. New sources of herbicide resistance are needed for crops so that herbicides can be rotated or combined to thwart the evolution of resistant weeds. The diverse family of cytochrome P450 proteins has been suggested to be a source of detoxifying herbicide metabolism in both weed and crop plants, and better understanding of these genes will offer avenues for crop improvement and novel weed management practices. Here, we report the identification of CYP749A16 (Gh_D10G1401) which is responsible for the natural tolerance exhibited by most cotton cultivars to the Envoke herbicide trifloxysulfuron sodium. A 1-bp frameshift insertion in CYP749A16 results in Envoke herbicide sensitivity. This allele perfectly co-segregated with the phenotype in 2145 F₂ progeny of the susceptible cultivar Paymaster HS26 crossed with the tolerant Stoneville 474, and in 550 recombinant inbred lines of a multi-parent advanced generation inter-cross population. Analysis of 382 additional cotton cultivars identified twelve containing the 1-bp insertion. Individual genotyping and phenotyping of plants from these twelve cultivars confirmed the genetic association. Virus induced gene silencing of CYP749A16 generated sensitivity in the resistant cotton cultivar Stoneville 474. Transformation of Arabidopsis with GhCYP749A16 did not generate herbicide resistance, which may be related to the loss of the entire CYP749 family in Arabidopsis. Taken together, we conclude that CYP749A16 is required for Envoke herbicide resistance in cotton, but is not sufficient for resistance in Arabidopsis.