title: Differences in shoot Na+ accumulation between two tomato species are due to differences in ion affinity of HKT1;2.
abstract: HKT1 has been shown to be essential in Na(+) homeostasis in plants. In this paper, we report the analysis of Na(+) accumulation in different plant organs of two tomato species with contrasting salt tolerances: Solanum lycopersicum and Solanum pennellii. Furthermore, we relate these differences in Na(+) accumulation between the two species to the differences in HKT1;2 transport kinetics and HKT1;2 expression. S. lycopersicum showed "Na(+) excluder" behaviour, whereas S. pennellii showed "Na(+) includer" behaviour. SlHKT1;2 expression, in contrast to SpHKT1;2 expression showed a significant effect of NaCl treatment, especially stems had a high increase in SlHKT1;2 expression. SlHKT1;2 promoter-GUS reporter gene analysis showed that SlHKT1;2 is expressed in the vasculature surrounding the roots and shoots of transformed Arabidopsis plants. In this paper, we present HKT1;2 protein sequences of both tomato species and provide evidence that both SlHKT1;2 and SpHKT1;2 are Na(+) transporters. Our kinetic studies showed that SpHKT1;2, in comparison with SlHKT1;2, had a lower affinity for Na(+). This low affinity of SpHKT1;2 correlated with higher xylem Na(+) and higher accumulation of Na(+) in stems and leaves of S. pennellii. Our findings demonstrate the importance of the understanding of transport characteristics of HKT1;2 transporters to improve the understanding of Na(+) homeostasis in plants.
authors.affiliation: Vrije Universiteit, Faculty of Earth and Life Sciences, Department of Structural Biology, Room H057, De Boelelaan 1081-1087, 1081 HV Amsterdam, The Netherlands. Electronic address: p.m.fidalgodealmeida@vu.nl.
authors.forename: Pedro
authors.initials: P
authors.lastname: Almeida
authors.affiliation: Enza Zaden, Oosterdijk Gebouw, P.O. Box 7, 1600 AA Enkhuizen, The Netherlands.
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: de Boer
authors.affiliation: Vrije Universiteit, Faculty of Earth and Life Sciences, Department of Structural Biology, Room H057, De Boelelaan 1081-1087, 1081 HV Amsterdam, The Netherlands.
authors.forename: Albertus H
authors.initials: AH
authors.lastname: de Boer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D018551:Solanum lycopersicum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D033661:Oocysts; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011188:Potassium / Q000032:analysis / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013045:Species Specificity; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus; D052584:Xylem / Q000235:genetics / Q000378:metabolism
chemical_list: D027682:Cation Transport Proteins; C088864:HKT1 protein, plant; D010940:Plant Proteins; D027981:Symporters; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium
keywords: HKT1 ;2 transporter; Salt tolerance; Solanum lycopersicum; Solanum pennellii