title: A mechanism of growth inhibition by abscisic acid in germinating seeds of Arabidopsis thaliana based on inhibition of plasma membrane H+-ATPase and decreased cytosolic pH, K+, and anions.
abstract: The stress hormone abscisic acid (ABA) induces expression of defence genes in many organs, modulates ion homeostasis and metabolism in guard cells, and inhibits germination and seedling growth. Concerning the latter effect, several mutants of Arabidopsis thaliana with improved capability for H(+) efflux (wat1-1D, overexpression of AKT1 and ost2-1D) are less sensitive to inhibition by ABA than the wild type. This suggested that ABA could inhibit H(+) efflux (H(+)-ATPase) and induce cytosolic acidification as a mechanism of growth inhibition. Measurements to test this hypothesis could not be done in germinating seeds and we used roots as the most convenient system. ABA inhibited the root plasma-membrane H(+)-ATPase measured in vitro (ATP hydrolysis by isolated vesicles) and in vivo (H(+) efflux from seedling roots). This inhibition involved the core ABA signalling elements: PYR/PYL/RCAR ABA receptors, ABA-inhibited protein phosphatases (HAB1), and ABA-activated protein kinases (SnRK2.2 and SnRK2.3). Electrophysiological measurements in root epidermal cells indicated that ABA, acting through the PYR/PYL/RCAR receptors, induced membrane hyperpolarization (due to K(+) efflux through the GORK channel) and cytosolic acidification. This acidification was not observed in the wat1-1D mutant. The mechanism of inhibition of the H(+)-ATPase by ABA and its effects on cytosolic pH and membrane potential in roots were different from those in guard cells. ABA did not affect the in vivo phosphorylation level of the known activating site (penultimate threonine) of H(+)-ATPase in roots, and SnRK2.2 phosphorylated in vitro the C-terminal regulatory domain of H(+)-ATPase while the guard-cell kinase SnRK2.6/OST1 did not.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: María D
authors.initials: MD
authors.lastname: Planes
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Regina
authors.initials: R
authors.lastname: Niñoles
authors.affiliation: Departamento de Biología Vegetal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Rubio
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Bissoli
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Bueso
authors.affiliation: Departamento de Biología Vegetal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: García-Sánchez
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Alejandro
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Gonzalez-Guzmán
authors.affiliation: Institute for Plant Physiology and Biophysics, University Würzburg, Julis-von-Sachs Platz 2, D-97082, Würzburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain.
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodriguez
authors.affiliation: Departamento de Biología Vegetal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Fernández
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Camino de Vera, 46022 Valencia, Spain rserrano@ibmcp.upv.es.
authors.forename: Ramón
authors.initials: R
authors.lastname: Serrano
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D007477:Ions / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002712:Chlorides; D007477:Ions; D000040:Abscisic Acid; D006180:Proton-Translocating ATPases; C544444:AHA1 protein, Arabidopsis; D011188:Potassium
keywords: ABA receptors; cytosolic pH; ion channels; microelectrodes; protein kinase; proton efflux.