title: A bacterial-type ABC transporter is involved in aluminum tolerance in rice.
abstract: Aluminum (Al) toxicity is a major factor limiting crop production in acidic soil, but the molecular mechanisms of Al tolerance are poorly understood. Here, we report that two genes, STAR1 (for sensitive to Al rhizotoxicity1) and STAR2, are responsible for Al tolerance in rice. STAR1 encodes a nucleotide binding domain, while STAR2 encodes a transmembrane domain, of a bacterial-type ATP binding cassette (ABC) transporter. Disruption of either gene resulted in hypersensitivity to aluminum toxicity. Both STAR1 and STAR2 are expressed mainly in the roots and are specifically induced by Al exposure. Expression in onion epidermal cells, rice protoplasts, and yeast showed that STAR1 interacts with STAR2 to form a complex that localizes to the vesicle membranes of all root cells, except for those in the epidermal layer of the mature zone. When expressed together in Xenopus laevis oocytes, STAR1/2 shows efflux transport activity specific for UDP-glucose. Furthermore, addition of exogenous UDP-glucose rescued root growth in the star1 mutant exposed to Al. These results indicate that STAR1 and STAR2 form a complex that functions as an ABC transporter, which is required for detoxification of Al in rice. The ABC transporter transports UDP-glucose, which may be used to modify the cell wall.
authors.affiliation: Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Chao Feng
authors.initials: CF
authors.lastname: Huang
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamaji
authors.forename: Namiki
authors.initials: N
authors.lastname: Mitani
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yano
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nagamura
authors.forename: Jian Feng
authors.initials: JF
authors.lastname: Ma
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000535:Aluminum / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000032:analysis; D019697:Onions / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000032:analysis; D014982:Xenopus laevis / Q000235:genetics; D015003:Yeasts / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000535:Aluminum