title: A plastidial sodium-dependent pyruvate transporter.
abstract: Pyruvate serves as a metabolic precursor for many plastid-localized biosynthetic pathways, such as those for fatty acids, terpenoids and branched-chain amino acids. In spite of the importance of pyruvate uptake into plastids (organelles within cells of plants and algae), the molecular mechanisms of this uptake have not yet been explored. This is mainly because pyruvate is a relatively small compound that is able to passively permeate lipid bilayers, which precludes accurate measurement of pyruvate transport activity in reconstituted liposomes. Using differential transcriptome analyses of C(3) and C(4) plants of the genera Flaveria and Cleome, here we have identified a novel gene that is abundant in C(4) species, named BASS2 (BILE ACID:SODIUM SYMPORTER FAMILY PROTEIN 2). The BASS2 protein is localized at the chloroplast envelope membrane, and is highly abundant in C(4) plants that have the sodium-dependent pyruvate transporter. Recombinant BASS2 shows sodium-dependent pyruvate uptake activity. Sodium influx is balanced by a sodium:proton antiporter (NHD1), which was mimicked in recombinant Escherichia coli cells expressing both BASS2 and NHD1. Arabidopsis thaliana bass2 mutants lack pyruvate uptake into chloroplasts, which affects plastid-localized isopentenyl diphosphate synthesis, as evidenced by increased sensitivity of such mutants to mevastatin, an inhibitor of cytosolic isopentenyl diphosphate biosynthesis. We thus provide molecular evidence for a sodium-coupled metabolite transporter in plastid envelopes. Orthologues of BASS2 can be detected in all the genomes of land plants that have been characterized so far, thus indicating the widespread importance of sodium-coupled pyruvate import into plastids.
authors.affiliation: Graduate School of Science, Hiroshima University, 1-3-1, Kagamiyama, Higashi-Hiroshima, 739-8526, Japan. tfurumoto@hiroshima-u.ac.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Furumoto
authors.forename: Teppei
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Ohshima-Ichie
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Tsuchida-Iwata
authors.forename: Masaki
authors.initials: M
authors.lastname: Shimamura
authors.forename: Junichi
authors.initials: J
authors.lastname: Ohnishi
authors.forename: Shingo
authors.initials: S
authors.lastname: Hata
authors.forename: Udo
authors.initials: U
authors.lastname: Gowik
authors.forename: Peter
authors.initials: P
authors.lastname: Westhoff
authors.forename: Andrea
authors.initials: A
authors.lastname: Bräutigam
authors.forename: Andreas P M
authors.initials: AP
authors.lastname: Weber
authors.forename: Katsura
authors.initials: K
authors.lastname: Izui
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D037142:Flaveria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D027981:Symporters; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; C000629170:BASS2 protein, Arabidopsis; D060365:Chloroplast Proteins; D026901:Membrane Transport Proteins; D027501:Monocarboxylic Acid Transporters; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D027981:Symporters; D019289:Pyruvic Acid; D012964:Sodium