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Updated: Apr 27, 2026

Author Spotlight: Image-Based Methods to Study Membrane Trafficking Events in Stomatal Lineage Cells
Published on: May 12, 2023
Phosphorylation of the vacuolar anion exchanger AtCLCa is required for the stomatal response to abscisic acid
Stefanie Wege1, Alexis De Angeli2, Marie-Jo Droillard1
1CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France.
Abstract:
Eukaryotic anion/proton exchangers of the CLC (chloride channel) family mediate anion fluxes across intracellular membranes. The Arabidopsis thaliana anion/proton exchanger AtCLCa is involved in vacuolar accumulation of nitrate. We investigated the role of AtCLCa in leaf guard cells, a specialized plant epidermal cell that controls gas exchange and water loss through pores called stomata. We showed that AtCLCa not only fulfilled the expected role of accumulating anions in the vacuole during stomatal opening but also mediated anion release during stomatal closure in response to the stress hormone abscisic acid (ABA). We found that this dual role resulted from a phosphorylation-dependent change in the activity of AtCLCa. The protein kinase OST1 (also known as SnRK2.6) is a key signaling player and central regulator in guard cells in response to ABA. Phosphorylation of Thr(38) in the amino-terminal cytoplasmic domain of AtCLCa by OST1 increased the outward anion fluxes across the vacuolar membrane, which are essential for stomatal closure. We provide evidence that bidirectional activities of an intracellular CLC exchanger are physiologically relevant and that phosphorylation regulates the transport mode of this exchanger.
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