title: The twins K+ and Na+ in plants.
abstract: In the earth's crust and in seawater, K(+) and Na(+) are by far the most available monovalent inorganic cations. Physico-chemically, K(+) and Na(+) are very similar, but K(+) is widely used by plants whereas Na(+) can easily reach toxic levels. Indeed, salinity is one of the major and growing threats to agricultural production. In this article, we outline the fundamental bases for the differences between Na(+) and K(+). We present the foundation of transporter selectivity and summarize findings on transporters of the HKT type, which are reported to transport Na(+) and/or Na(+) and K(+), and may play a central role in Na(+) utilization and detoxification in plants. Based on the structural differences in the hydration shells of K(+) and Na(+), and by comparison with sodium channels, we present an ad hoc mechanistic model that can account for ion permeation through HKTs.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: Begoña
authors.initials: B
authors.lastname: Benito
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Haro
authors.affiliation: Institute of Molecular, Cellular and Systems Biology (MCSB), College of Medical, Veterinary and Life Sciences (MVLS), University of Glasgow, Glasgow, UK.
authors.forename: Anna
authors.initials: A
authors.lastname: Amtmann
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, Montpellier, France.
authors.forename: Tracey Ann
authors.initials: TA
authors.lastname: Cuin
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain. Electronic address: ingo.dreyer@upm.es.
authors.forename: Ingo
authors.initials: I
authors.lastname: Dreyer
mesh_terms: D001692:Biological Transport; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D010940:Plant Proteins; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium
keywords: HKT; Potassium; Sodium; Transport mechanism