title: The K+/H+ antiporter LeNHX2 increases salt tolerance by improving K+ homeostasis in transgenic tomato.
abstract: The endosomal LeNHX2 ion transporter exchanges H(+) with K(+) and, to lesser extent, Na(+) . Here, we investigated the response to NaCl supply and K(+) deprivation in transgenic tomato (Solanum lycopersicum L.) overexpressing LeNHX2 and show that transformed tomato plants grew better in saline conditions than untransformed controls, whereas in the absence of K(+) the opposite was found. Analysis of mineral composition showed a higher K(+) content in roots, shoots and xylem sap of transgenic plants and no differences in Na(+) content between transgenic and untransformed plants grown either in the presence or the absence of 120 mm NaCl. Transgenic plants showed higher Na(+)/H(+) and, above all, K(+)/H(+) transport activity in root intracellular membrane vesicles. Under K(+) limiting conditions, transgenic plants enhanced root expression of the high-affinity K(+) uptake system HAK5 compared to untransformed controls. Furthermore, tomato overexpressing LeNHX2 showed twofold higher K(+) depletion rates and half cytosolic K(+) activity than untransformed controls. Under NaCl stress, transgenic plants showed higher uptake velocity for K(+) and lower cytosolic K(+) activity than untransformed plants. These results indicate the fundamental role of K(+) homeostasis in the better performance of LeNHX2 overexpressing tomato under NaCl stress.
authors.affiliation: Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Calle Profesor Albareda, 1, 18008, Granada, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Huertas
authors.forename: Lourdes
authors.initials: L
authors.lastname: Rubio
authors.forename: Olivier
authors.initials: O
authors.lastname: Cagnac
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: García-Sánchez
authors.forename: Juan De Dios
authors.initials: Jde D
authors.lastname: Alché
authors.forename: Kees
authors.initials: K
authors.lastname: Venema
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Fernández
authors.forename: María Pilar
authors.initials: MP
authors.lastname: Rodríguez-Rosales
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects / Q000235:genetics; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics; D030821:Plants, Genetically Modified; D011188:Potassium / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011522:Protons; D055049:Salt Tolerance / Q000187:drug effects / Q000235:genetics; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors
chemical_list: D017920:Antiporters; D010940:Plant Proteins; D011522:Protons; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium
keywords: K+ uptake; Na+ and K+ homeostasis; Solanum lycopersicum (tomato); cytosolic K+; salinity tolerance.