title: Two different effects of calcium on aquaporins in salinity-stressed pepper plants.
abstract: Two different effects of calcium were studied, respectively, in plasma membrane vesicles and in protoplasts isolated from roots of control pepper plants (Capsicum annuum L cv. California) or of plants treated with 50 mM NaCl, 10 mM CaCl(2) or 10 mM CaCl(2) + 50 mM NaCl. Under saline conditions, osmotic water permeability (P ( f )) values decreased in protoplasts and plasma membrane vesicles, and the same reduction was observed in the PIP1 aquaporin abundance, indicating inhibitory effects of NaCl on aquaporin functionality and protein abundance. The cytosolic Ca(2+) concentration, [Ca(2+)](cyt), was reduced by salinity, as observed by confocal microscope analysis. Two different actions of Ca(2+) were observed. On the one hand, increase in free cytosolic calcium concentrations associated with stress perception may lead to aquaporin closure. On the other hand, when critical requirements of Ca(2+) were reduced (by salinity), and extra-calcium would lead to an upregulation of aquaporins, indicating that a positive role of calcium at whole plant level combined with an inhibitory mechanism at aquaporin level may work in the regulation of pepper root water transport under salt stress. However, a link between these observations and other cell signalling in relation to water channel gating remains to be established.
authors.affiliation: Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura-CSIC, Apdo. Correos 164, 30100, Espinardo, Murcia, Spain.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Martínez-Ballesta
authors.forename: Francisco
authors.initials: F
authors.lastname: Cabañero
authors.forename: Enrique
authors.initials: E
authors.lastname: Olmos
authors.forename: Paula María
authors.initials: PM
authors.lastname: Periago
authors.forename: Christophe
authors.initials: C
authors.lastname: Maurel
authors.forename: Micaela
authors.initials: M
authors.lastname: Carvajal
mesh_terms: D020346:Aquaporins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002122:Calcium Chloride / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D004586:Electrophoresis; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D018613:Microscopy, Confocal; D009997:Osmotic Pressure / Q000187:drug effects; D029222:Piper nigrum / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D020346:Aquaporins; D010940:Plant Proteins; D012965:Sodium Chloride; D002122:Calcium Chloride; D002118:Calcium