title: Flavone glucoside uptake into barley mesophyll and Arabidopsis cell culture vacuoles. Energization occurs by H(+)-antiport and ATP-binding cassette-type mechanisms.
abstract: In many cases, secondary plant products accumulate in the large central vacuole of plant cells. However, the mechanisms involved in the transport of secondary compounds are only poorly understood. Here, we demonstrate that the transport mechanisms for the major barley (Hordeum vulgare) flavonoid saponarin (apigenin 6-C-glucosyl-7-O-glucoside) are different in various plant species: Uptake into barley vacuoles occurs via a proton antiport and is competitively inhibited by isovitexin (apigenin 6-C-glucoside), suggesting that both flavone glucosides are recognized by the same transporter. In contrast, the transport into vacuoles from Arabidopsis, which does not synthesize flavone glucosides, displays typical characteristics of ATP-binding cassette transporters. Transport of saponarin into vacuoles of both the species is saturable with a K(m) of 50 to 100 microM. Furthermore, the uptake of saponarin into vacuoles from a barley mutant exhibiting a strongly reduced flavone glucoside biosynthesis is drastically decreased when compared with the parent variety. Thus, the barley vacuolar flavone glucoside/H(+) antiporter could be modulated by the availability of the substrate. We propose that different vacuolar transporters may be responsible for the sequestration of species-specific/endogenous and nonspecific/xenobiotic secondary compounds in planta.
authors.affiliation: Institut de Botanique, Laboratoire de Physiologie Végétale, Université de Neuchâtel, Rue Emile Argand 13, CH-2007 Neuchâtel, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Frangne
authors.forename: Thomas
authors.initials: T
authors.lastname: Eggmann
authors.forename: Carsten
authors.initials: C
authors.lastname: Koblischke
authors.forename: Gottfried
authors.initials: G
authors.lastname: Weissenböck
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Markus
authors.initials: M
authors.lastname: Klein
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000502:physiology*; D047310:Apigenin; D017360:Arabidopsis / Q000378:metabolism*; D001693:Biological Transport, Active / Q000502:physiology; D002478:Cells, Cultured; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism*; D001467:Hordeum / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D047311:Luteolin; D018515:Plant Leaves / Q000378:metabolism; D014316:Tritium; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D005419:Flavonoids; D005960:Glucosides; D014316:Tritium; C457771:saponarin; D047310:Apigenin; C057912:homoorientin; C049772:isovitexin; D047311:Luteolin