biostudies-literatureCorso MEuropean Molecular Biology OrganizationMinistero dell&apos;Istruzione, dell&apos;Università e della RicercaFonds De La Recherche Scientifique - FNRS3966-3971https://www.ebi.ac.uk/biostudies/studies/S-EPMC5899463biostudies-literatureUnknown115(15)Ca²⁺ signals in plant cells are important for adaptive responses to environmental stresses. Here, we report that the <i>Arabidopsis</i> CATION/Ca²⁺ EXCHANGER2 (CCX2), encoding a putative cation/Ca²⁺ exchanger that localizes to the endoplasmic reticulum (ER), is strongly induced by salt and osmotic stresses. Compared with the WT, <i>AtCCX2</i> loss-of-function mutant was less tolerant to osmotic stress and displayed the most noteworthy phenotypes (less root/shoot growth) during salt stress. Conversely, <i>AtCCX2</i> gain-of-function mutants were more tolerant to osmotic stress. In addition, <i>AtCCX2</i> partially suppresses the Ca²⁺ sensitivity of K667 yeast triple mutant, characterized by Ca²⁺ uptake deficiency. Remarkably, Cameleon Ca²⁺ sensors revealed that the absence of AtCCX2 activity results in decreased cytosolic and increased ER Ca²⁺ concentrations in comparison with both WT and the gain-of-function mutants. This was observed in both salt and nonsalt osmotic stress conditions. It appears that AtCCX2 is directly involved in the control of Ca²⁺ fluxes between the ER and the cytosol, which plays a key role in the ability of plants to cope with osmotic stresses. To our knowledge, <i>Atccx2</i> is unique as a plant mutant to show a measured alteration in ER Ca²⁺ concentrations. In this study, we identified the ER-localized AtCCX2 as a pivotal player in the regulation of ER Ca²⁺ dynamics that heavily influence plant growth upon salt and osmotic stress.Proceedings of the National Academy of Sciences of the United States of AmericaEndoplasmic reticulum-localized CCX2 is required for osmotolerance by regulating ER and cytosolic Ca²⁺ dynamics in <i>Arabidopsis</i>.PMC5899463ASTF 604-2015RBFR10S1LJ_001PDR T.0206.13Doccula FGCosta AVerbruggen NCorso Mde Melo JRFfalseEndoplasmic reticulum-localized CCX2 is required for osmotolerance by regulating ER and cytosolic Ca²⁺ dynamics in <i>Arabidopsis</i>.Ca²⁺ signals in plant cells are important for adaptive responses to environmental stresses. Here, we report that the <i>Arabidopsis</i> CATION/Ca²⁺ EXCHANGER2 (CCX2), encoding a putative cation/Ca²⁺ exchanger that localizes to the endoplasmic reticulum (ER), is strongly induced by salt and osmotic stresses. Compared with the WT, <i>AtCCX2</i> loss-of-function mutant was less tolerant to osmotic stress and displayed the most noteworthy phenotypes (less root/shoot growth) during salt stress. Conversely, <i>AtCCX2</i> gain-of-function mutants were more tolerant to osmotic stress. In addition, <i>AtCCX2</i> partially suppresses the Ca²⁺ sensitivity of K667 yeast triple mutant, characterized by Ca²⁺ uptake deficiency. Remarkably, Cameleon Ca²⁺ sensors revealed that the absence of AtCCX2 activity results in decreased cytosolic and increased ER Ca²⁺ concentrations in comparison with both WT and the gain-of-function mutants. This was observed in both salt and nonsalt osmotic stress conditions. It appears that AtCCX2 is directly involved in the control of Ca²⁺ fluxes between the ER and the cytosol, which plays a key role in the ability of plants to cope with osmotic stresses. To our knowledge, <i>Atccx2</i> is unique as a plant mutant to show a measured alteration in ER Ca²⁺ concentrations. In this study, we identified the ER-localized AtCCX2 as a pivotal player in the regulation of ER Ca²⁺ dynamics that heavily influence plant growth upon salt and osmotic stress.2018-01-01T00:00:00Z2018 Apr2024-12-04T10:37:50.649Z2019-03-26T23:59:42ZS-EPMC58994632958127710.1073/pnas.1720422115