Atrazine (ATZ) residue in farmland is one of the environmental contaminants seriously affecting crop production and food safety. Understanding the regulatory mechanism for ATZ metabolism and degradation in plants is important to help reduce ATZ potential toxicity to both plants and human health. Here, we report our newly developed engineered rice overexpressing a novel Phase II metabolic enzyme glycosyltransfearse1 (ARGT1) responsible for transformation of ATZ residues in rice. Our results showed that transformed lines, when exposed to environmentally realistic ATZ concentration (0.2-0.8 mg/L), displayed significantly high tolerance, with 8-27% biomass and 36-56% chlorophyll content higher, but 37-69% plasma membrane injury lower than untransformed lines. Such results were well confirmed by ARGT1 expression in Arabidopsis. ARGT1-transformed rice took up 1.6-2.7 fold ATZ from its growth medium compared to its wild type (WT) and accumulated ATZ 10%-43% less than that of WT. A long-term study also showed that ATZ in the grains of ARGT1-transformed rice was reduced by 30-40% compared to WT. The ATZ-degraded products were characterized by UPLC/Q-TOF-MS/MS. More ATZ metabolites and conjugates accumulated in ARGT1-transformed rice than in WT. Eight ATZ metabolites for Phase I reaction and 10 conjugates for Phase II reaction in rice were identified, with three ATZ-glycosylated conjugates that have never been reported before. These results indicate that ARGT1 expression can facilitate uptake of ATZ from environment and metabolism in rice plants.

Accumulating pesticide (and herbicide) residues in soils have become a serious environmental problem. This study focused on identifying the removal of two widely used pesticides, isoproturon (IPU) and acetochlor (ACT), by a genetically developed paddy (or rice) plant overexpressing an uncharacterized glycosyltransferase (IRGT1). IRGT1 conferred plant resistance to isoproturon–acetochlor, which was manifested by attenuated cellular injury and alleviated toxicity of rice under isoproturon–acetochlor stress. A short-term study showed that IRGT1-transformed lines removed 33.3–48.3% of isoproturon and 39.8–53.5% of acetochlor from the growth medium, with only 59.5–72.1 and 58.9–70.4% of the isoproturon and acetochlor remaining in the plants compared with the levels in untransformed rice. This phenotype was confirmed by IRGT1-expression in yeast (Pichia pastoris) which grew better and contained less isoproturon–acetochlor than the control cells. A long-term study showed that isoproturon–acetochlor concentrations at all developmental stages were significantly lower in the transformed rice, which contain only 59.3–69.2% (isoproturon) and 51.7–57.4% (acetochlor) of the levels in wild type. In contrast, UPLC-Q-TOF-MS/MS analysis revealed that more isoproturon–acetochlor metabolites were detected in the transformed rice. Sixteen metabolites of isoproturon and 19 metabolites of acetochlor were characterized in rice for Phase I reactions, and 9 isoproturon and 13 acetochlor conjugates were characterized for Phase II reactions in rice; of these, 7 isoproturon and 6 acetochlor metabolites and conjugates were reported in plants for the first time.

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