title: Diversity in expression patterns and functional properties in the rice HKT transporter family.
abstract: Plant growth under low K(+) availability or salt stress requires tight control of K(+) and Na(+) uptake, long-distance transport, and accumulation. The family of membrane transporters named HKT (for High-Affinity K(+) Transporters), permeable either to K(+) and Na(+) or to Na(+) only, is thought to play major roles in these functions. Whereas Arabidopsis (Arabidopsis thaliana) possesses a single HKT transporter, involved in Na(+) transport in vascular tissues, a larger number of HKT transporters are present in rice (Oryza sativa) as well as in other monocots. Here, we report on the expression patterns and functional properties of three rice HKT transporters, OsHKT1;1, OsHKT1;3, and OsHKT2;1. In situ hybridization experiments revealed overlapping but distinctive and complex expression patterns, wider than expected for such a transporter type, including vascular tissues and root periphery but also new locations, such as osmocontractile leaf bulliform cells (involved in leaf folding). Functional analyses in Xenopus laevis oocytes revealed striking diversity. OsHKT1;1 and OsHKT1;3, shown to be permeable to Na(+) only, are strongly different in terms of affinity for this cation and direction of transport (inward only or reversible). OsHKT2;1 displays diverse permeation modes, Na(+)-K(+) symport, Na(+) uniport, or inhibited states, depending on external Na(+) and K(+) concentrations within the physiological concentration range. The whole set of data indicates that HKT transporters fulfill distinctive roles at the whole plant level in rice, each system playing diverse roles in different cell types. Such a large diversity within the HKT transporter family might be central to the regulation of K(+) and Na(+) accumulation in monocots.
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, UMR 5004 CNRS/INRA/SupAgro-M/UM2, Campus SupAgro-M/INRA, 34060 Montpellier cedex 1, France.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Jabnoune
authors.forename: Sandra
authors.initials: S
authors.lastname: Espeout
authors.forename: Delphine
authors.initials: D
authors.lastname: Mieulet
authors.forename: Cécile
authors.initials: C
authors.lastname: Fizames
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Verdeil
authors.forename: Geneviève
authors.initials: G
authors.lastname: Conéjéro
authors.forename: Alonso
authors.initials: A
authors.lastname: Rodríguez-Navarro
authors.forename: Hervé
authors.initials: H
authors.lastname: Sentenac
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Guiderdoni
authors.forename: Chedly
authors.initials: C
authors.lastname: Abdelly
authors.forename: Anne-Aliénor
authors.initials: AA
authors.lastname: Véry
mesh_terms: D000818:Animals; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D012275:Oryza / Q000166:cytology / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics; D011188:Potassium / Q000378:metabolism; D021381:Protein Transport; D012964:Sodium / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; D012964:Sodium; D011188:Potassium