Fenoxaprop-P-ethyl resistance in Alopecurus aequalis: Involvement of GSTF13 in addition to Ile-1781-Leu mutation.

Shortawn foxtail (Alopecurus aequalis Sobol.) is a challenging weed species to manage in wheat production systems globally. In prior research, we identified a field population of A. aequalis (Aa-R) that had developed resistance to the widely used acetolactate synthase (ALS)-inhibiting herbicide mesosulfuron-methyl. In this study, we found that the Aa-R population also exhibited significant resistance to the acetyl-CoA carboxylase (ACCase)-inhibiting herbicide fenoxaprop-P-ethyl and showed broad-spectrum resistance to other three ACCase-inhibiting herbicides, haloxyfop-P-methyl, clodinafop-propargyl, clethodim, and pinoxaden. Sequence analysis of the ACCase gene revealed the presence of a known resistance mutation (Ile-1781-Leu) in the Aa-R population. Pretreatment with the GST inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) decreased the resistance to fenoxaprop-P-ethyl in the Aa-R population. We amplified an upregulated GST gene in the Aa-R population, designated AaGSTF13. Transgenic rice calli and seedlings overexpressing AaGSTF13 exhibited resistance specifically to fenoxaprop-P-ethyl, and might enhance reactive oxygen species (ROS) scavenging capacity. Further transcriptome analyses suggested that the expressions of genes associated with ROS scavenging was upregulated in transgenic plants. Our results indicate that AaGSTF13 enhances detoxification metabolism and could potentially enhances ROS scavenging in transgenic rice, which might contribute to enhanced herbicide resistance. These findings suggest that AaGSTF13 represents a promising candidate gene for the genetic improvement of new rice varieties under herbicide stress conditions.