Paraquat is one of the most widely used nonselective herbicides and has elicited the emergence of paraquat-resistant weeds. However, the molecular mechanisms of paraquat resistance are not completely understood. Here we report the Arabidopsis gain-of-function mutant pqt15-D with significantly enhanced resistance to paraquat and the corresponding gene PQT15, which encodes the Multidrug and Toxic Extrusion (MATE) transporter DTX6. A point mutation at +932 bp in DTX6 causes a G311E amino acid substitution, enhancing the paraquat resistance of pqt15-D, and overexpression of DTX6/PQT15 in the wild-type plants also results in strong paraquat resistance. Moreover, heterologous expression of DTX6 and DTX6-D in Escherichia coli significantly enhances bacterial resistance to paraquat. Importantly, overexpression of DTX6-D enables Arabidopsis plants to tolerate 4 mM paraquat, a near-commercial application level. DTX6/PQT15 is localized in the plasma membrane and endomembrane, and functions as a paraquat efflux transporter as demonstrated by paraquat efflux assays with isolated protoplasts and bacterial cells. Taken together, our results demonstrate that DTX6/PQT15 is an efflux transporter that confers paraquat resistance by exporting paraquat out of the cytosol. These findings reveal a molecular mechanism of paraquat resistance in higher plants and provide a promising candidate gene for engineering paraquat-resistant crops.

百草枯是使用最广泛的非选择性除草剂之一，并引发了抗百草枯杂草的出现。然而，百草枯抗性的分子机制尚不完全清楚。在这里，我们报告了拟南芥功能获得性突变体pqt15-D对百草枯和相应基因PQT15的抗性显着增强，该基因编码多药和有毒挤出 (MATE) 转运蛋白 DTX6。DTX6 中+932 bp 的点突变导致 G311E 氨基酸取代，增强pqt15-D的百草枯抗性和DTX6/PQT15的过表达在野生型植物中也导致了对百草枯的强烈抗性。此外，DTX6和DTX6-D在大肠杆菌中的异源表达显着增强了细菌对百草枯的抗性。重要的是，DTX6-D的过表达使拟南芥成为可能植物耐受 4 mM 百草枯，接近商业应用水平。DTX6/PQT15 定位于质膜和内膜，并作为百草枯外排转运蛋白发挥作用，百草枯外排分析表明，使用分离的原生质体和细菌细胞。总之，我们的研究结果表明，DTX6/PQT15 是一种外排转运蛋白，可通过将百草枯从胞质溶胶中输出来赋予百草枯抗性。这些发现揭示了高等植物中百草枯抗性的分子机制，并为工程抗百草枯作物提供了一个有希望的候选基因。