title: Tonoplast CBL-CIPK calcium signaling network regulates magnesium homeostasis in Arabidopsis.
abstract: Although Mg(2+) is essential for a myriad of cellular processes, high levels of Mg(2+) in the environment, such as those found in serpentine soils, become toxic to plants. In this study, we identified two calcineurin B-like (CBL) proteins, CBL2 and CBL3, as key regulators for plant growth under high-Mg conditions. The Arabidopsis mutant lacking both CBL2 and CBL3 displayed severe growth retardation in the presence of excess Mg(2+), implying elevated Mg(2+) toxicity in these plants. Unexpectedly, the cbl2 cbl3 mutant plants retained lower Mg content than wild-type plants under either normal or high-Mg conditions, suggesting that CBL2 and CBL3 may be required for vacuolar Mg(2+) sequestration. Indeed, patch-clamp analysis showed that the cbl2 cbl3 mutant exhibited reduced Mg(2+) influx into the vacuole. We further identified four CBL-interacting protein kinases (CIPKs), CIPK3, -9, -23, and -26, as functionally overlapping components downstream of CBL2/3 in the signaling pathway that facilitates Mg(2+) homeostasis. The cipk3 cipk9 cipk23 cipk26 quadruple mutant, like the cbl2 cbl3 double mutant, was hypersensitive to high-Mg conditions; furthermore, CIPK3/9/23/26 physically interacted with CBL2/3 at the vacuolar membrane. Our results thus provide evidence that CBL2/3 and CIPK3/9/23/26 constitute a multivalent interacting network that regulates the vacuolar sequestration of Mg(2+), thereby protecting plants from Mg(2+) toxicity.
authors: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
authors: Ren-Jie
authors: RJ
authors: Tang
authors: Nanjing University-Nanjing Forestry University Joint Institute for Plant Molecular Biology, State Key Laboratory for Pharmaceutical Biotechnology, College of Life Sciences, Nanjing University, Nanjing 210093, China; and.
authors: Fu-Geng
authors: FG
authors: Zhao
authors: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
authors: Veder J
authors: VJ
authors: Garcia
authors: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
authors: Thomas J
authors: TJ
authors: Kleist
authors: Nanjing University-Nanjing Forestry University Joint Institute for Plant Molecular Biology, State Key Laboratory for Pharmaceutical Biotechnology, College of Life Sciences, Nanjing University, Nanjing 210093, China; and.
authors: Lei
authors: L
authors: Yang
authors: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors: Hong-Xia
authors: HX
authors: Zhang
authors: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; Nanjing University-Nanjing Forestry University Joint Institute for Plant Molecular Biology, State Key Laboratory for Pharmaceutical Biotechnology, College of Life Sciences, Nanjing University, Nanjing 210093, China; and sluan@berkeley.edu.
authors: Sheng
authors: S
authors: Luan
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D006706:Homeostasis; D008274:Magnesium / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C417306:CBL protein, Arabidopsis; D002135:Calcium-Binding Proteins; C507144:CIPK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D008274:Magnesium
keywords: calcium sensor; magnesium toxicity; magnesium transport; vacuole
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