title: Characterization of Two HKT1;4 Transporters from Triticum monococcum to Elucidate the Determinants of the Wheat Salt Tolerance Nax1 QTL.
abstract: TmHKT1;4-A1 and TmHKT1;4-A2 are two Na+transporter genes that have been identified as associated with the salt tolerance Nax1 locus found in a durum wheat (Triticum turgidum L. subsp. durum) line issued from a cross with T. monococcum. In the present study, we were interested in getting clues on the molecular mechanisms underpinning this salt tolerance quantitative trait locus (QTL). By analyzing the phylogenetic relationships between wheat and T. monococcum HKT1;4-type genes, we found that durum and bread wheat genomes possess a close homolog of TmHKT1;4-A1, but no functional close homolog of TmHKT1;4-A2. Furthermore, performing real-time reverse transcription-PCR experiments, we showed that TmHKT1;4-A1 and TmHKT1;4-A2 are similarly expressed in the leaves but that TmHKT1;4-A2 is more strongly expressed in the roots, which would enable it to contribute more to the prevention of Na+transfer to the shoots upon salt stress. We also functionally characterized the TmHKT1;4-A1 and TmHKT1;4-A2 transporters by expressing them in Xenopus oocytes. The two transporters displayed close functional properties (high Na+/K+selectivity, low affinity for Na+, stimulation by external K+of Na+transport), but differed in some quantitative parameters: Na+affinity was 3-fold lower and the maximal inward conductance was 3-fold higher in TmHKT1;4-A2 than in TmHKT1;4-A1. The conductance of TmHKT1;4-A2 at high Na+concentration (>10 mM) was also shown to be higher than that of the two durum wheat HKT1;4-type transporters so far characterized. Altogether, these data support the hypothesis that TmHKT1;4-A2 is responsible for the Nax1 trait and provide new insight into the understanding of this QTL.
authors.affiliation: Biotechnology and Plant Improvement Laboratory, Centre of Biotechnology of Sfax (CBS)/University of Sfax, BP '1177', 3018 Sfax, Tunisia.|Biochimie & Physiologie Moléculaire des plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France.
authors.forename: Sana
authors.initials: S
authors.lastname: Tounsi
authors.affiliation: Biotechnology and Plant Improvement Laboratory, Centre of Biotechnology of Sfax (CBS)/University of Sfax, BP '1177', 3018 Sfax, Tunisia.|Biochimie & Physiologie Moléculaire des plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France.
authors.forename: Siwar
authors.initials: S
authors.lastname: Ben Amar
authors.affiliation: Biotechnology and Plant Improvement Laboratory, Centre of Biotechnology of Sfax (CBS)/University of Sfax, BP '1177', 3018 Sfax, Tunisia.|Present address: International Center for Biosaline Agriculture (ICBA), PO Box 14660, Dubai-United Arab Emirates.
authors.forename: Khaled
authors.initials: K
authors.lastname: Masmoudi
authors.affiliation: Biochimie & Physiologie Moléculaire des plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Sentenac
authors.affiliation: Biotechnology and Plant Improvement Laboratory, Centre of Biotechnology of Sfax (CBS)/University of Sfax, BP '1177', 3018 Sfax, Tunisia.
authors.forename: Faiçal
authors.initials: F
authors.lastname: Brini
authors.affiliation: Biochimie & Physiologie Moléculaire des plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France very@supagro.inra.fr.
authors.forename: Anne-Aliénor
authors.initials: AA
authors.lastname: Véry
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002412:Cations; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D040641:Quantitative Trait Loci / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D055049:Salt Tolerance / Q000187:drug effects / Q000235:genetics*; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D014908:Triticum / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D014981:Xenopus
chemical_list: D027682:Cation Transport Proteins; D002412:Cations; D010940:Plant Proteins; D012965:Sodium Chloride; D012964:Sodium
keywords: 
  Nax1 salt tolerance QTL; 
  Triticum monococcum
  ; 
  Xenopus oocyte; HKT1;4; Sodium transport; qRT-PCR