NtPDR1, a Plasma Membrane ABC Transporter from Nicotiana Tabacum, is Involved in Diterpene Transport

ATP-binding cassette transporters are involved in the active transport of a wide variety of metabolites in prokaryotes and eukaryotes. One subfamily, the Pleiotropic Drug Resistance (PDR) transporters, or full-size ABCG transporters, are found only in fungi and plants. NtPDR1 was originally identified in Nicotiana tabacum suspension cells (BY2), in which its expression was induced by microbial elicitors. To obtain information on its expression in plants, we generated NtPDR1-specific antibodies and, using Western blotting, found that this transporter is localized in roots, leaves, and flowers and this was confirmed in transgenic plants expressing the ß-glucuronidase reporter gene fused to the NtPDR1 promoter region. Expression was seen in the lateral roots and in the long glandular trichomes of the leaves, stem, and flowers. Western blot analysis and in situ immunolocalization showed NtPDR1 to be localized in the plasma membrane. Induction of NtPDR1 expression by various compounds was tested in N. tabacum BY2 cells. Induction of expression was observed with the hormones methyl jasmonate and naphthalene acetic acid and diterpenes. Constitutive ectopic expression of NtPDR1 in N. tabacum BY2 cells resulted in increased resistance to several diterpenes. Transport tests directly demonstrated the ability of NtPDR1 to transport diterpenes. These data suggest that NtPDR1 is involved in plant defense through diterpene transport.