title: Aquaporins Contribute to ABA-Triggered Stomatal Closure through OST1-Mediated Phosphorylation.
abstract: Stomatal movements in response to environmental stimuli critically control the plant water status. Although these movements are governed by osmotically driven changes in guard cell volume, the role of membrane water channels (aquaporins) has remained hypothetical. Assays in epidermal peels showed that knockout Arabidopsis thaliana plants lacking the Plasma membrane Intrinsic Protein 2;1 (PIP2;1) aquaporin have a defect in stomatal closure, specifically in response to abscisic acid (ABA). ABA induced a 2-fold increase in osmotic water permeability (Pf) of guard cell protoplasts and an accumulation of reactive oxygen species in guard cells, which were both abrogated in pip2;1 plants. Open stomata 1 (OST1)/Snf1-related protein kinase 2.6 (SnRK2.6), a protein kinase involved in guard cell ABA signaling, was able to phosphorylate a cytosolic PIP2;1 peptide at Ser-121. OST1 enhanced PIP2;1 water transport activity when coexpressed in Xenopus laevis oocytes. Upon expression in pip2;1 plants, a phosphomimetic form (Ser121Asp) but not a phosphodeficient form (Ser121Ala) of PIP2;1 constitutively enhanced the Pf of guard cell protoplasts while suppressing its ABA-dependent activation and was able to restore ABA-dependent stomatal closure in pip2;1. This work supports a model whereby ABA-triggered stomatal closure requires an increase in guard cell permeability to water and possibly hydrogen peroxide, through OST1-dependent phosphorylation of PIP2;1 at Ser-121.
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004, CNRS/INRA/Montpellier SupAgro/Université Montpellier, F-34060 Montpellier, Cedex 2, France.
authors.forename: Alexandre
authors.identifier: http://orcid.org/0000-0001-6726-6274
authors.initials: A
authors.lastname: Grondin
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004, CNRS/INRA/Montpellier SupAgro/Université Montpellier, F-34060 Montpellier, Cedex 2, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Rodrigues
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004, CNRS/INRA/Montpellier SupAgro/Université Montpellier, F-34060 Montpellier, Cedex 2, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Verdoucq
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Sciences Plant Saclay, F-91198 Gif sur Yvette Cedex, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Merlot
authors.affiliation: Laboratoire de Biologie du Développement des Plantes, CEA Cadarache, Unité Mixte de Recherche 7265, CNRS/CEA/Aix-Marseille Université, F-13108 Saint-Paul-lez-Durance, France.
authors.forename: Nathalie
authors.identifier: http://orcid.org/0000-0002-5392-9732
authors.initials: N
authors.lastname: Leonhardt
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004, CNRS/INRA/Montpellier SupAgro/Université Montpellier, F-34060 Montpellier, Cedex 2, France maurel@supagro.inra.fr.
authors.forename: Christophe
authors.identifier: http://orcid.org/0000-0002-4255-6440
authors.initials: C
authors.lastname: Maurel
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000818:Animals; D020346:Aquaporins / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005816:Genetic Complementation Test; D009068:Movement / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D054046:Plant Stomata / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism*; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014981:Xenopus
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; C491680:plasma membrane intrinsic protein 2 Arabidopsis; D010768:Phosphoserine; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis