title: High Ca(2+) reverts the repression of high-affinity K(+) uptake produced by Na(+) in Solanum lycopersycum L. (var. microtom) plants.
abstract: Potassium (K(+)) is an essential nutrient for plants which is acquired by plant roots through the operation of specific transport systems. Abiotic stress conditions such as salinity impair K(+) nutrition because, in addition to other effects, high salt concentrations in the solution bathing the roots inhibit K(+) uptake systems. This detrimental effect of salinity is exacerbated when external K(+) is very low and the only system capable of mediating K(+) uptake is one with high-affinity for K(+), as that mediated by transporters of the HAK5 type. Increasing external Ca(2+) has been shown to improve K(+) nutrition under salinity and, although the specific mechanisms for this beneficial effect are largely unknown, they are beginning to be understood. The genes encoding the HAK5 transporters are induced by K(+) starvation and repressed by long-term exposure to high Na(+). This occurs in parallel with the hyperpolarization and depolarization of root cell membrane potential. In the present study it is shown in tomato plants that the presence of high Ca(2+) during the K(+) starvation period that leads to LeHAK5 induction, counteracts the repression exerted by high Na(+). High Ca(2+) reduces the Na(+)-induced plasma membrane depolarization of root cells, resorting one of the putative first steps in the low-K(+) signal cascade. This allows proper LeHAK5 expression and functional high-affinity K(+) uptake at the roots. Thus, the maintenance of HAK5-mediated K(+) nutrition under salinity by high Ca(2+) can be regarded as a specific beneficial effect of Ca(2+) contributing to salt tolerance in plants.
authors.affiliation: Department of Plant Nutrition, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia Spain.
authors.forename: Hayet
authors.initials: H
authors.lastname: Bacha
authors.affiliation: Department of Plant Nutrition, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia Spain.
authors.forename: Reyes
authors.initials: R
authors.lastname: Ródenas
authors.affiliation: EPSO Universidad Miguel Hernández, Ctra de Beniel, Km 3.2., 03312 Orihuela, Alicante, Spain.
authors.forename: Elvira
authors.initials: E
authors.lastname: López-Gómez
authors.affiliation: EPSO Universidad Miguel Hernández, Ctra de Beniel, Km 3.2., 03312 Orihuela, Alicante, Spain.
authors.forename: Manuel Francisco
authors.initials: MF
authors.lastname: García-Legaz
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, 34060 Montpellier Cedex 2, France.
authors.forename: Manuel
authors.initials: M
authors.lastname: Nieves-Cordones
authors.affiliation: Department of Plant Nutrition, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia Spain.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Rivero
authors.affiliation: Department of Plant Nutrition, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Martínez
authors.affiliation: EPSO Universidad Miguel Hernández, Ctra de Beniel, Km 3.2., 03312 Orihuela, Alicante, Spain.
authors.forename: M Ángeles
authors.initials: MÁ
authors.lastname: Botella
authors.affiliation: Department of Plant Nutrition, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia Spain. Electronic address: frubio@cebas.csic.es.
authors.forename: Francisco
authors.initials: F
authors.lastname: Rubio
mesh_terms: D064751:Ammonium Compounds / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D059828:Plant Cells / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D012996:Solutions
chemical_list: D064751:Ammonium Compounds; D010940:Plant Proteins; D012996:Solutions; D001464:Barium; D012964:Sodium; D011188:Potassium; D002118:Calcium
keywords: Calcium; High-affinity K(+) uptake; LeHAK5; Membrane potential; Salinity