Wege Stefanie, De Angeli Alexis, Droillard Marie-Jo, Kroniewicz Laetitia, Merlot Sylvain, Cornu David, Gambale Franco, Martinoia Enrico, Barbier-Brygoo Hélène, Thomine Sébastien, Leonhardt Nathalie, Filleur Sophie
CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France.
CNRS-UPR 2355, Institut des Sciences du Végétal, Saclay Plant Sciences Labex, Bât. 22, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France. Istituto di Biofisica, C.N.R., Via De Marini 6, 16149 Genova, Italy. Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
Sci Signal. 2014 Jul 8;7(333):ra65. doi: 10.1126/scisignal.2005140.
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.
CLC（氯离子通道）家族的真核阴离子/质子交换体介导阴离子跨细胞内膜的转运。拟南芥阴离子/质子交换体AtCLCa参与液泡中硝酸盐的积累。我们研究了AtCLCa在叶片保卫细胞中的作用，保卫细胞是一种特殊的植物表皮细胞，通过称为气孔的孔隙控制气体交换和水分流失。我们发现，AtCLCa不仅在气孔开放期间在液泡中积累阴离子发挥了预期作用，而且在气孔关闭期间响应胁迫激素脱落酸（ABA）介导阴离子释放。我们发现这种双重作用源于AtCLCa活性的磷酸化依赖性变化。蛋白激酶OST1（也称为SnRK2.6）是保卫细胞中响应ABA的关键信号分子和核心调节因子。OST1对AtCLCa氨基末端胞质结构域中Thr(38)的磷酸化增加了跨液泡膜的外向阴离子通量，这对气孔关闭至关重要。我们提供的证据表明，细胞内CLC交换体的双向活性具有生理相关性，并且磷酸化调节该交换体的转运模式。
