Chengbin Xiang
University of Science and Technology of China

Paraquat is one of the most widely used herbicides in the world. However, its transporter has not been isolated in plants. Here we report a paraquat tolerant mutant pqt24-1 isolated from an activation tagging library for its tolerance to 2 ?M paraquat in the seedling stage. Molecular analysis revealed that the T-DNA was inserted in the thirteenth exon of AT1G66950 encoding AtPDR11, a member of the ATP-binding cassette transporter superfamily. As a result, AtPDR11 was knocked out in the mutant. Loss-of-function mutations of AtPDR11 led to a reduced paraquat accumulation in plant cells. In addition, AtPDR11 protein was specifically localized in the plasmalemma, suggesting AtPDR11 as a potential transporter of paraquat. This was supported by kinetic analysis of paraquat import. Further studies showed that the transcript level of AtPDR11 could be strongly induced by paraquat and other abiotic stresses including H2O2, indicating a possible up-regulation of AtPDR11 expression by oxidative stress signaling. Thus, our data suggest that paraquat is a substrate of AtPDR11 and the enhanced paraquat tolerance of pqt24-1 is due to the reduced uptake of paraquat into plant cells.