title: HKT2;2/1, a K⁺-permeable transporter identified in a salt-tolerant rice cultivar through surveys of natural genetic polymorphism.
abstract: We have investigated OsHKT2;1 natural variation in a collection of 49 cultivars with different levels of salt tolerance and geographical origins. The effect of identified polymorphism on OsHKT2;1 activity was analysed through heterologous expression of variants in Xenopus oocytes. OsHKT2;1 appeared to be a highly conserved protein with only five possible amino acid substitutions that have no substantial effect on functional properties. Our study, however, also identified a new HKT isoform, No-OsHKT2;2/1 in Nona Bokra, a highly salt-tolerant cultivar. No-OsHKT2;2/1 probably originated from a deletion in chromosome 6, producing a chimeric gene. Its 5' region corresponds to that of OsHKT2;2, whose full-length sequence is not present in Nipponbare but has been identified in Pokkali, a salt-tolerant rice cultivar. Its 3' region corresponds to that of OsHKT2;1. No-OsHKT2;2/1 is essentially expressed in roots and displays a significant level of expression at high Na⁺ concentrations, in contrast to OsHKT2;1. Expressed in Xenopus oocytes or in Saccharomyces cerevisiae, No-OsHKT2;2/1 exhibited a strong permeability to Na⁺ and K⁺, even at high external Na⁺ concentrations, like OsHKT2;2, and in contrast to OsHKT2;1. Our results suggest that No-OsHKT2;2/1 can contribute to Nona Bokra salt tolerance by enabling root K⁺ uptake under saline conditions.
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: Ronald J F J
authors.initials: RJ
authors.lastname: Oomen
authors.forename: Begoña
authors.initials: B
authors.lastname: Benito
authors.forename: Hervé
authors.initials: H
authors.lastname: Sentenac
authors.forename: Alonso
authors.initials: A
authors.lastname: Rodríguez-Navarro
authors.forename: Manuel
authors.initials: M
authors.lastname: Talón
authors.forename: Anne-Aliénor
authors.initials: AA
authors.lastname: Véry
authors.forename: Concha
authors.initials: C
authors.lastname: Domingo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011188:Potassium / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D055049:Salt Tolerance / Q000235:genetics*; D055051:Salt-Tolerant Plants / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D027981:Symporters / Q000378:metabolism; D014981:Xenopus
chemical_list: D027682:Cation Transport Proteins; C434985:HKT2 protein, Oryza sativa; D010940:Plant Proteins; D027981:Symporters; D012964:Sodium; D011188:Potassium