Loss of AtPDR11, a plasma membrane-localized ABC transporter, confers paraquat tolerance inArabidopsis thaliana

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Paraquat is one of the most widely used herbicides in the world. However, no paraquat transporter has been isolated in plants. Here, we describe paraquat-tolerant mutantpqt24-1, isolated from an activation-tagging library on the basis of its tolerance to 2 μM paraquat in the seedling stage. Molecular analysis revealed that the T-DNA was inserted in the 13th exon ofAt1g66950, which encodes AtPDR11, a member of the ATP-binding cassette transporter superfamily. As a result,AtPDR11was knocked out in the mutant. Loss-of-function mutations ofAtPDR11led to reduced paraquat accumulation in plant cells. In addition, the AtPDR11 protein was specifically localized in the plasmalemma, suggesting AtPDR11 as a potential transporter of paraquat. This conclusion was supported by kinetic analysis of paraquat import. Further studies showed that the transcript level ofAtPDR11could be strongly induced by paraquat and other abiotic stresses including H2O2, indicating possible up-regulation ofAtPDR11expression by oxidative stress signaling. Thus, our data suggest that paraquat is an opportunistic substrate of AtPDR11 and the enhanced paraquat tolerance ofpqt24-1is due to reduced uptake of paraquat into plant cells.

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