title: Characterization of Coptis japonica CjABCB2, an ATP-binding cassette protein involved in alkaloid transport.
abstract: Higher plants produce a large number of secondary metabolites. Among these are the alkaloids, a group of small nitrogen-containing molecules. Alkaloids often have strong biological activity that protects alkaloid-producing plants from herbivores, and often accumulate to high concentrations in a specific organelle of a particular organ in the producing plant. However, knowledge of the membrane transport mechanism of alkaloids is still limited. Coptis japonica, a perennial Ranunculaceous plant, produces the benzylisoquinoline alkaloid berberine. This alkaloid, though biosynthesized in root tissues, accumulates in the rhizome, suggesting translocation of the molecule via xylem. In this study, a gene encoding a ATP-binding cassette (ABC) protein of B-type, Cjabcb2, was isolated from C. japonica. Northern analysis showed that Cjabcb2 was preferentially expressed in the rhizome, which is the sink organ of berberine. Functional analysis of CjABCB2 using yeast suggested that CjABCB2 transports berberine in an inward direction. Membrane separation and in situ hybridization data indicated that CjABCB2 might be involved in translocation of berberine from the root to the rhizome by transporting berberine at the plasma membrane of cells around the xylem of the rhizome.
authors.affiliation: Laboratory of Plant Gene Expression, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Japan.
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Shitan
authors.forename: Fabien
authors.initials: F
authors.lastname: Dalmas
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Dan
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Kato
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Ueda
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
authors.forename: Cyrille
authors.initials: C
authors.lastname: Forestier
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000470:Alkaloids / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D002478:Cells, Cultured; D039323:Coptis / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D000470:Alkaloids; D010940:Plant Proteins; D012333:RNA, Messenger