Abstract
Plants contain a large number of ATP-binding cassette (ABC) transporters belonging to different subclasses. AtPDR8 is the only member of the pleiotropic drug resistance ABC transporter (PDR) subclass in Arabidopsis that is constitutively highly expressed. Subcellular fractionation and immunochemical analysis showed that AtPDR8 was localized in the plasma membrane. When a knockout mutant of AtPDR8 (atpdr8) was infected with bacterial and oomycete pathogens, the plants exhibited chlorotic lesions and hypersensitive response (HR)-like cell death. The growth of virulent Pseudomonas syringae in the leaves of the atpdr8 mutant was reduced to 1% of that in the wild type. The defense response genes, PR-1, PR-2, PR-5, VPEg, AtrbohD, and AtrbohF were highly expressed in atpdr8 mutants. Our results indicate that AtPDR8 is a key factor controlling the extent of cell death in HR and suggest that AtPDR8 transports some substance(s), which is closely related to the response of plants to pathogens.
