title: AtALMT9 is a malate-activated vacuolar chloride channel required for stomatal opening in Arabidopsis.
abstract: Water deficit strongly affects crop productivity. Plants control water loss and CO2 uptake by regulating the aperture of the stomatal pores within the leaf epidermis. Stomata aperture is regulated by the two guard cells forming the pore and changing their size in response to ion uptake and release. While our knowledge about potassium and chloride fluxes across the plasma membrane of guard cells is advanced, little is known about fluxes across the vacuolar membrane. Here we present the molecular identification of the long-sought-after vacuolar chloride channel. AtALMT9 is a chloride channel activated by physiological concentrations of cytosolic malate. Single-channel measurements demonstrate that this activation is due to a malate-dependent increase in the channel open probability. Arabidopsis thaliana atalmt9 knockout mutants exhibited impaired stomatal opening and wilt more slowly than the wild type. Our findings show that AtALMT9 is a vacuolar chloride channel having a major role in controlling stomata aperture.
authors: Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland. deangeli.alexis@gmail.com
authors: Alexis
authors: A
authors: De Angeli
authors: Jingbo
authors: J
authors: Zhang
authors: Stefan
authors: S
authors: Meyer
authors: Enrico
authors: E
authors: Martinoia
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D003600:Cytosol; D007425:Intracellular Membranes / Q000378:metabolism; D015640:Ion Channel Gating; D008293:Malates / Q000378:metabolism*; D058503:Mesophyll Cells / Q000378:metabolism; D008954:Models, Biological; D010539:Permeability; D054046:Plant Stomata / Q000502:physiology*; D011523:Protoplasts / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
chemical_list: C584418:ALMT9 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018118:Chloride Channels; D002712:Chlorides; D008293:Malates
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