Overexpressing of GT8 confers resistance to fenoxaprop-P-ethyl in Alopecurus japonicus.

Background: Alopecurus japonicus is one of the most predominant weeds in wheat fields across China, where significant herbicide resistance has emerged over the past decade.

Results: When compared to the susceptible (S) population, the resistant (R) population exhibited a 9.48-fold increase in resistance to fenoxaprop-P-ethyl. The R population displayed cross-resistance to haloxyfop-P-methyl, quizalofop-P-ethyl, clodinafop-propargyl, sethoxydim, clethodim and pinoxaden. No known resistance mutations or overexpression of ACCase were detected in the R population. The R population showed enhanced metabolism of fenoxaprop-P-ethyl, as evidenced by high-performance liquid chromatography analysis. The cytochrome P450 (CYP450) inhibitor malathion and the glutathione-S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) partially reversed resistance to fenoxaprop-P-ethyl in the R population. Six upregulated genes were identified via RNA-sequencing, including two CYP450 genes (CYP86B1 and CYP71C1), one GST gene (GSTT1) and three glycosyl transferase (GT) genes (UGT73C, GT8 and CGT). Specifically, the expression of GT8 in yeast decreased sensitivity to fenoxaprop-P-ethyl, suggesting its potential involvement in herbicide metabolism. Molecular docking analysis further suggests that GT8 may be involved in herbicide metabolism.

Conclusion: Our findings not only identified GT8 as partially responsible for the resistance of A. japonicus to fenoxaprop-P-ethyl, but also provide a valuable resource for crop genetic engineering. These insights also could inform the development of effective management strategies for A. japonicus. © 2025 Society of Chemical Industry.