title: Mutations in the hyperosmotic stress-responsive mitochondrial BASIC AMINO ACID CARRIER2 enhance proline accumulation in Arabidopsis.
abstract: Mitochondrial carrier family proteins are diverse in their substrate specificity, organellar location, and gene expression. In Arabidopsis (Arabidopsis thaliana), 58 genes encode these six-transmembrane-domain proteins. We investigated the biological role of the basic amino acid carrier Basic Amino Acid Carrier2 (BAC2) from Arabidopsis that is structurally and functionally similar to ARG11, a yeast ornithine and arginine carrier, and to Arabidopsis BAC1. By studying the expression of BAC2 and the consequences of its mutation in Arabidopsis, we showed that BAC2 is a genuine mitochondrial protein and that Arabidopsis requires expression of the BAC2 gene in order to use arginine. The BAC2 gene is induced by hyperosmotic stress (with either 0.2 m NaCl or 0.4 m mannitol) and dark-induced senescence. The BAC2 promoter contains numerous stress-related cis-regulatory elements, and the transcriptional activity of BAC2:beta-glucuronidase is up-regulated by stress and senescence. Under hyperosmotic stress, bac2 mutants express the P5CS1 proline biosynthetic gene more strongly than the wild type, and this correlates with a greater accumulation of Pro. Our data suggest that BAC2 is a hyperosmotic stress-inducible transporter of basic amino acids that contributes to proline accumulation in response to hyperosmotic stress in Arabidopsis.
authors.affiliation: Laboratoire de Physiologie Cellulaire et Moléculaire des Plantes, Université Pierre et Marie Curie (Paris 6), UR5 EAC7180 CNRS, Case 156, 75005 Paris, France.
authors.forename: Iman
authors.initials: I
authors.lastname: Toka
authors.forename: Séverine
authors.initials: S
authors.lastname: Planchais
authors.forename: Cécile
authors.initials: C
authors.lastname: Cabassa
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Justin
authors.forename: Delphine
authors.initials: D
authors.lastname: De Vos
authors.forename: Luc
authors.initials: L
authors.lastname: Richard
authors.forename: Arnould
authors.initials: A
authors.lastname: Savouré
authors.forename: Pierre
authors.initials: P
authors.lastname: Carol
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009997:Osmotic Pressure; D011392:Proline / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D026923:Amino Acid Transport Systems, Basic; D029681:Arabidopsis Proteins; C515230:Bac2 protein, Arabidopsis; D011392:Proline