title: The Na+ transporter AtHKT1;1 controls retrieval of Na+ from the xylem in Arabidopsis.
abstract: HKT-type transporters appear to play key roles in Na(+) accumulation and salt sensitivity in plants. In Arabidopsis HKT1;1 has been proposed to influx Na(+) into roots, recirculate Na(+) in the phloem and control root : shoot allocation of Na(+). We tested these hypotheses using (22)Na(+) flux measurements and ion accumulation assays in an hkt1;1 mutant and demonstrated that AtHKT1;1 contributes to the control of both root accumulation of Na(+) and retrieval of Na(+) from the xylem, but is not involved in root influx or recirculation in the phloem. Mathematical modelling indicated that the effects of the hkt1;1 mutation on root accumulation and xylem retrieval were independent. Although AtHKT1;1 has been implicated in regulation of K(+) transport and the hkt1;1 mutant showed altered net K(+) accumulation, (86)Rb(+) uptake was unaffected by the hkt1;1 mutation. The hkt1;1 mutation has been shown previously to rescue growth of the sos1 mutant on low K(+); however, HKT1;1 knockout did not alter K(+) or (86)Rb(+) accumulation in sos1.
authors.affiliation: Department of Plant Sciences, Downing Street, Cambridge CB2 3EA, UK. romola.davenport@ageing.ox.ac.uk
authors.forename: Romola Jane
authors.initials: RJ
authors.lastname: Davenport
authors.forename: Alicia
authors.initials: A
authors.lastname: Muñoz-Mayor
authors.forename: Deepa
authors.initials: D
authors.lastname: Jha
authors.forename: Pauline Adobea
authors.initials: PA
authors.lastname: Essah
authors.forename: Ana
authors.initials: A
authors.lastname: Rus
authors.forename: Mark
authors.initials: M
authors.lastname: Tester
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D018527:Hydroponics; D017136:Ion Transport / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D018517:Plant Roots / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology; D027981:Symporters / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000378:metabolism; D052584:Xylem / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; C490286:HKT1 protein, Arabidopsis; C477653:SOS1 protein, Arabidopsis; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; D012964:Sodium; D011188:Potassium