title: The AtNHX1 exchanger mediates potassium compartmentation in vacuoles of transgenic tomato.
abstract: NHX-type antiporters in the tonoplast have been reported to increase the salt tolerance of various plants species, and are thought to mediate the compartmentation of Na(+) in vacuoles. However, all isoforms characterized so far catalyze both Na(+)/H(+) and K(+)/H(+) exchange. Here, we show that AtNHX1 has a critical involvement in the subcellular partitioning of K(+), which in turn affects plant K(+) nutrition and Na(+) tolerance. Transgenic tomato plants overexpressing AtNHX1 had larger K(+) vacuolar pools in all growth conditions tested, but no consistent enhancement of Na(+) accumulation was observed under salt stress. Plants overexpressing AtNHX1 have a greater capacity to retain intracellular K(+) and to withstand salt-shock. Under K(+)-limiting conditions, greater K(+) compartmentation in the vacuole occurred at the expense of the cytosolic K(+) pool, which was lower in transgenic plants. This caused the early activation of the high-affinity K(+) uptake system, enhanced K(+) uptake by roots, and increased the K(+) content in plant tissues and the xylem sap of transformed plants. Our results strongly suggest that NHX proteins are likely candidates for the H(+)-linked K(+) transport that is thought to facilitate active K(+) uptake at the tonoplast, and the partitioning of K(+) between vacuole and cytosol.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología (IRNASE), Consejo Superior de Investigaciones Científicas, Reina Mercedes, 10, Sevilla - 41012, Spain.
authors.forename: Eduardo O
authors.initials: EO
authors.lastname: Leidi
authors.forename: Verónica
authors.initials: V
authors.lastname: Barragán
authors.forename: Lourdes
authors.initials: L
authors.lastname: Rubio
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: El-Hamdaoui
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Ruiz
authors.forename: Beatriz
authors.initials: B
authors.lastname: Cubero
authors.forename: José A
authors.initials: JA
authors.lastname: Fernández
authors.forename: Ray A
authors.initials: RA
authors.lastname: Bressan
authors.forename: Paul M
authors.initials: PM
authors.lastname: Hasegawa
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Quintero
authors.forename: José M
authors.initials: JM
authors.lastname: Pardo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011188:Potassium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; C117751:NHX1 protein, Arabidopsis; D017923:Sodium-Hydrogen Exchangers; D011188:Potassium