title: Vacuolar transport of nicotine is mediated by a multidrug and toxic compound extrusion (MATE) transporter in Nicotiana tabacum.
abstract: Alkaloids play a key role in plant defense mechanisms against pathogens and herbivores, but the plants themselves need to cope with their toxicity as well. The major alkaloid of the Nicotiana species, nicotine, is translocated via xylem transport from the root tissues where it is biosynthesized to the accumulation sites, the vacuoles of leaves. To unravel the molecular mechanisms behind this membrane transport, we characterized one transporter, the tobacco (Nicotiana tabacum) jasmonate-inducible alkaloid transporter 1 (Nt-JAT1), whose expression was coregulated with that of nicotine biosynthetic genes in methyl jasmonate-treated tobacco cells. Nt-JAT1, belonging to the family of multidrug and toxic compound extrusion transporters, was expressed in roots, stems, and leaves, and localized in the tonoplast of leaf cells. When produced in yeast cells, Nt-JAT1 occurred mainly in the plasma membrane and showed nicotine efflux activity. Biochemical analysis with proteoliposomes reconstituted with purified Nt-JAT1 and bacterial F(0)F(1)-ATPase revealed that Nt-JAT1 functioned as a proton antiporter and recognized endogenous tobacco alkaloids, such as nicotine and anabasine, and other alkaloids, such as hyoscyamine and berberine, but not flavonoids. These findings strongly suggest that Nt-JAT1 plays an important role in the nicotine translocation by acting as a secondary transporter responsible for unloading of alkaloids in the aerial parts and deposition in the vacuoles.
authors.affiliation: Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji 611-0011, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Morita
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Shitan
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sawada
authors.forename: Marc C E
authors.initials: MC
authors.lastname: Van Montagu
authors.forename: Dirk
authors.initials: D
authors.lastname: Inzé
authors.forename: Heiko
authors.initials: H
authors.lastname: Rischer
authors.forename: Alain
authors.initials: A
authors.lastname: Goossens
authors.forename: Kirsi-Marja
authors.initials: KM
authors.lastname: Oksman-Caldentey
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
mesh_terms: D017920:Antiporters / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D003001:Cloning, Molecular; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008040:Genetic Linkage; D008954:Models, Biological; D008969:Molecular Sequence Data; D009538:Nicotine / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology*; D011510:Proteolipids / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000378:metabolism*
chemical_list: D017920:Antiporters; D010940:Plant Proteins; D011510:Proteolipids; C020485:proteoliposomes; D009538:Nicotine