title: A mitochondrial GABA permease connects the GABA shunt and the TCA cycle, and is essential for normal carbon metabolism.
abstract: In plants, γ-aminobutyric acid (GABA) accumulates in the cytosol in response to a variety of stresses. GABA is transported into mitochondria, where it is catabolized into TCA cycle or other intermediates. Although there is circumstantial evidence for mitochondrial GABA transporters in eukaryotes, none have yet been identified. Described here is an Arabidopsis protein similar in sequence and topology to unicellular GABA transporters. The expression of this protein complements a GABA-transport-deficient yeast mutant. Thus the protein was termed AtGABP to indicate GABA-permease activity. In vivo localization of GABP fused to GFP and immunobloting of subcellular fractions demonstrate its mitochondrial localization. Direct [(3) H]GABA uptake measurements into isolated mitochondria revealed impaired uptake into mitochondria of a gabp mutant compared with wild-type (WT) mitochondria, implicating AtGABP as a major mitochondrial GABA carrier. Measurements of CO(2) release, derived from radiolabeled substrates in whole seedlings and in isolated mitochondria, demonstrate impaired GABA-derived input into the TCA cycle, and a compensatory increase in TCA cycle activity in gabp mutants. Finally, growth abnormalities of gabp mutants under limited carbon availability on artificial media, and in soil under low light intensity, combined with their metabolite profiles, suggest an important role for AtGABP in primary carbon metabolism and plant growth. Thus, AtGABP-mediated transport of GABA from the cytosol into mitochondria is important to ensure proper GABA-mediated respiration and carbon metabolism. This function is particularly essential for plant growth under conditions of limited carbon.
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel.
authors.forename: Simon
authors.initials: S
authors.lastname: Michaeli
authors.forename: Aaron
authors.initials: A
authors.lastname: Fait
authors.forename: Kelly
authors.initials: K
authors.lastname: Lagor
authors.forename: Adriano
authors.initials: A
authors.lastname: Nunes-Nesi
authors.forename: Nicole
authors.initials: N
authors.lastname: Grillich
authors.forename: Ayelet
authors.initials: A
authors.lastname: Yellin
authors.forename: Dana
authors.initials: D
authors.lastname: Bar
authors.forename: Munziba
authors.initials: M
authors.lastname: Khan
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Turano
authors.forename: Hillel
authors.initials: H
authors.lastname: Fromm
mesh_terms: D000595:Amino Acid Sequence; D000704:Analysis of Variance; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015139:Blotting, Southern; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002952:Citric Acid Cycle; D003600:Cytosol / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D015151:Immunoblotting / Q000379:methods; D008027:Light; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000201:enzymology*; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D050485:GABA Plasma Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; D002245:Carbon Dioxide; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D002244:Carbon; D011392:Proline