title: Tonoplast calcium sensors CBL2 and CBL3 control plant growth and ion homeostasis through regulating V-ATPase activity in Arabidopsis.
abstract: Plant responses to developmental and environmental cues are often mediated by calcium (Ca(2+)) signals that are transmitted by diverse calcium sensors. The calcineurin B-like (CBL) protein family represents calcium sensors that decode calcium signals through specific interactions with a group of CBL-interacting protein kinases. We report functional analysis of Arabidopsis CBL2 and CBL3, two closely related CBL members that are localized to the vacuolar membrane through the N-terminal tonoplast-targeting sequence. While cbl2 or cbl3 single mutant did not show any phenotypic difference from the wild type, the cbl2 cbl3 double mutant was stunted with leaf tip necrosis, underdeveloped roots, shorter siliques and fewer seeds. These defects were reminiscent of those in the vha-a2 vha-a3 double mutant deficient in vacuolar H(+)-ATPase (V-ATPase). Indeed, the V-ATPase activity was reduced in the cbl2 cbl3 double mutant, connecting tonoplast CBL-type calcium sensors to the regulation of V-ATPase. Furthermore, cbl2 cbl3 double mutant was compromised in ionic tolerance and micronutrient accumulation, consistent with the defect in V-ATPase activity that has been shown to function in ion compartmentalization. Our results suggest that calcium sensors CBL2 and CBL3 serve as molecular links between calcium signaling and V-ATPase, a central regulator of intracellular ion homeostasis.
authors.affiliation: 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.forename: Ren-Jie
authors.initials: RJ
authors.lastname: Tang
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Xiao-Shu
authors.initials: XS
authors.lastname: Gao
authors.forename: Veder J
authors.initials: VJ
authors.lastname: Garcia
authors.forename: Sheng
authors.initials: S
authors.lastname: Luan
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002118:Calcium; D002135:Calcium-Binding Proteins; D025262:Vacuolar Proton-Translocating ATPases; C484079:CBL3 protein, Arabidopsis; C480758:At5g55990 protein, Arabidopsis