title: Evidence for GABA-Induced Systemic GABA Accumulation inArabidopsisupon Wounding.
abstract: The non-proteinogenic amino acid γ-aminobutyric acid (GABA) is present in all plant species analyzed so far. Its synthesis is stimulated by either acidic conditions occurring after tissue disruption or higher cytosolic calcium level. In mammals, GABA acts as inhibitory neurotransmitter but its function in plants is still not well understood. Besides its involvement in abiotic stress resistance, GABA has a role in the jasmonate-independent defense against invertebrate pests. While the biochemical basis for GABA accumulation in wounded leaves is obvious, the underlying mechanisms for wounding-induced GABA accumulation in systemic leaves remained unclear. Here, theArabidopsis thalianaknock-out mutant linespop2-5, unable to degrade GABA, andtpc1-2, lacking a wounding-induced systemic cytosolic calcium elevation, were employed for a comprehensive investigation of systemic GABA accumulation. A wounding-induced systemic GABA accumulation was detected intpc1-2plants demonstrating that an increased calcium level was not involved. Similarly, after both mechanical wounding andSpodoptera littoralisfeeding, GABA accumulation inpop2-5plants was significantly higher in local and systemic leaves, compared to wild-type plants. Consequently, larvae feeding on these GABA-enriched mutant plants grew significantly less. Upon exogenous application of a D2-labeled GABA to wounded leaves ofpop2-5plants, its uptake but no translocation to unwounded leaves was detected. In contrast, an accumulation of endogenous GABA was observed in vascular connected systemic leaves. These results suggest that the systemic accumulation of GABA upon wounding does not depend on the translocation of GABA or on an increase in cytosolic calcium.
authors.affiliation: Institute of General Botany and Plant Physiology, Friedrich Schiller University Jena, Germany.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Scholz
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical EcologyJena, Germany; Graduate Program in Cell and Molecular Biology, Biotechnology Center, Federal University of Rio Grande do SulPorto Alegre, Brazil.
authors.forename: Jaiana
authors.initials: J
authors.lastname: Malabarba
authors.affiliation: Department of Biochemistry, Max Planck Institute for Chemical Ecology Jena, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Reichelt
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology Jena, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Heyer
authors.affiliation: Division of Biochemistry, Department of Biology, University of Erlangen-Nuremberg Erlangen, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Ludewig
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology Jena, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Mithöfer
keywords: MecWorm; Spodoptera littoralis; calcium; herbivory; plant defense; systemic signaling; γ-aminobutyric acid