An ABCG-type transporter intensifies ametryn catabolism by Phase III reaction mechanism in rice

Pesticide residues in food crops are one of the seriously environmental contaminants that risk food safety and human health. Understanding the mechanism for pesticide catabolism is critical to develop effective biotechniques for rapid eliminating the residues in food crops. In this study we characterized a novel ABC transporter family gene ABCG52 (PDR18) in regulating rice response to pesticide ametryn (AME) widely used in the farmland. Efficient biodegradation of AME was evaluated by measuring its biotoxicity, accumulation, and metabolites in rice plants. OsPDR18 was localized to the plasma membrane and strongly induced under AME exposure. Transgenic rice overexpressing OsPDR18 (OE) conferred rice resistance and detoxification to AME by increasing chlorophyll contents, improving growth phenotypes, and reducing AME accumulation in plants. The AME concentrations in OE plants were only 71.8-78.1% (shoots) and 75.0-83.3% (roots) of the wild type. Mutation of OsPDR18 by CRISPR/Cas9 protocol led to the compromised growth and enhanced AME accumulation in rice. Five AME metabolites for Phase I and 13 conjugates for Phase II reactions in rice were characterized by HPLC/Q-TOF-HRMS/MS. Relative content analysis revealed that the AME metabolic products in OE plants were significantly reduced compared with wild-type. Importantly, the OE plants accumulated less AME metabolites and conjugates in rice grains, suggesting that OsPDR18 expression may actively facilitate the transport of AME for catabolism. These data unveil a AME catabolic mechanism by which OsPDR18 contributes to the AME detoxification and degradation in rice crops.