BsUGT74B1 confers Fenoxaprop-P-ethyl resistance through glycosylation and antioxidant regulation in Beckmannia syzigachne.

Beckmannia syzigachne is a dominant troublesome weed in wheat fields across China. Long-term continuous application of herbicides has led to widespread resistance of this weed to fenoxaprop-P-ethyl, a typical acetyl-CoA carboxylase (ACCase)-inhibiting herbicide, severely threatening wheat field weed management. In this study, we systematically clarified the resistance level and molecular mechanisms underlying fenoxaprop-P-ethyl resistance in a field-evolved resistant B. syzigachne population (R), which showed 5.26-fold resistance compared with the susceptible population (S). Target-site gene sequencing confirmed no resistance-related mutation in the ACCase coding region. Furthermore, resistance was not reversed by inhibitors of cytochrome P450 or glutathione S-transferase. RNA-Seq and RT-qPCR analyses identified a highly upregulated UDP-glycosyltransferase gene, BsUGT74B1. Heterologous overexpression of BsUGT74B1 in yeast and rice distinctly improved plant tolerance to fenoxaprop-P-ethyl. Liquid chromatography-mass spectrometry (LC-MS) and molecular docking demonstrated that BsUGT74B1 catalyzes the glycosylation of fenoxaprop-P-ethyl and binds stably to the herbicide. Moreover, BsUGT74B1 overexpression increased antioxidant capacity and reduced oxidative damage. Integrated transcriptomic and metabolomic analyses revealed that this gene modulates jasmonic acid biosynthesis and α-linolenic acid metabolism, thereby enhancing reactive oxygen species scavenging. In conclusion, BsUGT74B1 confers fenoxaprop-P-ethyl resistance in B. syzigachne via dual regulatory mechanisms including herbicide metabolic detoxification and enhanced oxidative stress tolerance.