Salt Stress Triggers Phosphorylation of the Arabidopsis Vacuolar K＋ Channel TPK1 by Calcium-Dependent Protein Kinases （CDPKs）  

作　　者：Andreas Latz Norbert Mehlmer Simone Zapf Thomas D. Mueller Bernhard Wurzinger Barbara Pfister Edina Csaszar Rainer Hedrich Markus Teige Dirk Becker 

机构地区：[1]Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-lnstitute, University of Wurzburg, Julius-von-Sachs-Platz 2, D-97082 Wurzburg, Germany [2]Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohrgasse 9, A-1030 Vienna, Austria [3]Present address: Department of Biology I, Botany, Munich Center for Integrated Protein Science CiPSM, Ludwig-Maximilians-Universitat Munchen D-82152 Planegg-Martinsried, Germany [4]College of Science, King Saud University, Riyadh 11451, Saudi Arabia

出　　处：《Molecular Plant》2013年第4期1274-1289,共16页分子植物（英文版）

基　　金：the Austrian Science Foundation (FWF) to M.T.，grants of the DFG to R.H.，T.D.M.，D.B.

摘　　要：14-3-3 proteins play an important role in the regulation of many cellular processes. The Arabidopsis vacuolar two-pore K＋ channel 1 （TPK1） interacts with the 14-3-3 protein GRF6 （GF14-λ）. Upon phosphorylation of the putative binding motif in the N-terminus of TPK1, GRF6 binds to TPK1 and activates the potassium channel. In order to gain a deeper understanding of this 14-3-3-mediated signal transduction, we set out to identify the respective kinases, which regulate the phosphorylation status of the 14-3-3 binding motif in TPK1. Here, we report that the calcium-dependent protein kinases （CDPKs） can phosphorylate and thereby activate the 14-3-3 binding motif in TPK1. Focusing on the stress-activated kinase CPK3, we visualized direct and specific interaction of TPK1 with the kinase at the tonoplast in vivo. In line with its proposed role in K＋ homeostasis, TPK1 phosphorylation was found to be induced by salt stress in planta, and both cpk3 and tpkl mutants displayed salt-sensitive phenotypes. Molecular modeling of the TPK1-CPK3 interaction domain provided mechanistic insights into TPK1 stress-regulated phosphorylation responses and pinpointed two arginine residues in the N-terminal 14-3-3 binding motif in TPK1 critical for kinase interaction. Taken together, our studies provide evidence for an essential role of the vacuolar potassium channel TPK1 in salt-stress adaptation as a target of calcium-regulated stress signaling pathways involving Ca2＋, Ca2＋-dependent kinases, and 14-3-3 proteins.14-3-3 proteins play an important role in the regulation of many cellular processes. The Arabidopsis vacuolar two-pore K＋ channel 1 （TPK1） interacts with the 14-3-3 protein GRF6 （GF14-λ）. Upon phosphorylation of the putative binding motif in the N-terminus of TPK1, GRF6 binds to TPK1 and activates the potassium channel. In order to gain a deeper understanding of this 14-3-3-mediated signal transduction, we set out to identify the respective kinases, which regulate the phosphorylation status of the 14-3-3 binding motif in TPK1. Here, we report that the calcium-dependent protein kinases （CDPKs） can phosphorylate and thereby activate the 14-3-3 binding motif in TPK1. Focusing on the stress-activated kinase CPK3, we visualized direct and specific interaction of TPK1 with the kinase at the tonoplast in vivo. In line with its proposed role in K＋ homeostasis, TPK1 phosphorylation was found to be induced by salt stress in planta, and both cpk3 and tpkl mutants displayed salt-sensitive phenotypes. Molecular modeling of the TPK1-CPK3 interaction domain provided mechanistic insights into TPK1 stress-regulated phosphorylation responses and pinpointed two arginine residues in the N-terminal 14-3-3 binding motif in TPK1 critical for kinase interaction. Taken together, our studies provide evidence for an essential role of the vacuolar potassium channel TPK1 in salt-stress adaptation as a target of calcium-regulated stress signaling pathways involving Ca2＋, Ca2＋-dependent kinases, and 14-3-3 proteins.

关 键 词：potassium channel VACUOLE CALCIUM calcium-dependent kinase 14-3-3 protein salt stress. 

分 类 号：Q73[生物学—分子生物学] S513.01[农业科学—作物学]