One Glutathione S-Transferase Gene, GSTU163, Was Involved in Mesosulfuron-methyl Resistance in Alopecurus japonicus

Alopecurus japonicus, an annual grass damaging wheat and canola fields in China, has evolved resistance to mesosulfuron-methyl, an acetolactate synthase (ALS)-inhibiting herbicide commonly used for its control. In this study, the resistant population (R) exhibited 22.93-fold resistance to mesosulfuron-methyl, and single-dose screening revealed cross-resistance to five other ALS-inhibiting herbicides. ALS gene sequencing revealed no known resistance mutations. Pretreatment with the glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) increased the sensitivity of the R population to mesosulfuron-methyl. RNA-seq and quantitative real-time polymerase chain reaction (RT-qPCR) identified significant upregulation of one cytochrome P450 gene, two GST genes, and three glycosyltransferase genes, with AjGSTU163 showing the highest upregulation in the R population. Heterologous expression of AjGSTU163 in yeast significantly enhanced growth on mesosulfuron-methyl-containing media by mitigating ROS accumulation. Knockout of rice homologue OsGSTU163 slightly increased sensitivity to mesosulfuron-methyl in rice. This study first reported that GST contributes to mesosulfuron-methyl resistance in A. japonicus.