Acetyltransferase OsACE2 acts as a regulator to reduce the environmental risk of oxyfluorfen to rice production.

The constant use of the pesticide oxyfluorfen (OFF) in farmland contaminates the soil, posing threats to crop growth and human health. To avoid the contamination of food crops with OFF, it is critically important to understand its absorption and degradation mechanisms. In this study, we characterized a new functional locus encoding an acetyltransferase (OsACE2) that can facilitate OFF degradation in rice. OsACE2 was drastically induced by OFF at 0.04-0.2 mg L for 6 days and the rice growth was significantly inhibited. To demonstrate the regulatory role of OsACE2 in resistance to OFF toxicity, we generated OsACE2 overexpression (OE) and knockout mutant using genetic transformation and gene-editing technologies (CRISPR/Cas9). The OE plants grown in the hydroponic medium showed improved growth (plant elongation and biomass), increased chlorophyll content, and reduced OFF-induced oxidative stress. The OsACE2-improved growth phenotypes of rice were attributed to the significantly lower OFF accumulation in OE plants. Conversely, knocking out OsACE2 resulted in compromised growth phenotypes compared to the wild-type (WT). Using LC-LTQ-HRMS/MS, five mono-metabolites and eleven conjugates of OFF were characterized through various canonical pathways, such as hydrolysis, oxidation, reduction, glycosylation, acetylation, malonylation, and interaction with amino acids. These metabolites increased in the OE plants, and five acetylated conjugates were reported for the first time. Collectively, OsACE2 plays a primary role in catabolizing OFF residues in rice through multiple degradation pathways and reducing OFF in its growth environment.