Mutations in the hyperosmotic stress-responsive mitochondrial BASIC AMINO ACID CARRIER2 enhance proline accumulation in Arabidopsis.
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.
Toka
Iman
I
Laboratoire de Physiologie Cellulaire et Moléculaire des Plantes, Université Pierre et Marie Curie (Paris 6), UR5 EAC7180 CNRS, Case 156, 75005 Paris, France.
Planchais
Séverine
S
Cabassa
Cécile
C
Justin
Anne-Marie
AM
De Vos
Delphine
D
Richard
Luc
L
Savouré
Arnould
A
Carol
Pierre
P
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
D026923:Amino Acid Transport Systems, Basic; D029681:Arabidopsis Proteins; C515230:Bac2 protein, Arabidopsis; D011392:Proline