Abstract
Cellular Na(+)/K(+) ratio is a crucial parameter determining plant salinity stress resistance. We tested the function of plasma membrane Na(+)/K(+) cotransporters in the High-affinity K(+) Transporter (HKT) family from the halophytic Arabidopsis (Arabidopsis thaliana) relative Thellungiella salsuginea. T. salsuginea contains at least two HKT genes. TsHKT1;1 is expressed at very low levels, while the abundant TsHKT1;2 is transcriptionally strongly up-regulated by salt stress. TsHKT-based RNA interference in T. salsuginea resulted in Na(+) sensitivity and K(+) deficiency. The athkt1 mutant lines overexpressing TsHKT1;2 proved less sensitive to Na(+) and showed less K(+) deficiency than lines overexpressing AtHKT1. TsHKT1;2 ectopically expressed in yeast mutants lacking Na(+) or K(+) transporters revealed strong K(+) transporter activity and selectivity for K(+) over Na(+). Altering two amino acid residues in TsHKT1;2 to mimic the AtHKT1 sequence resulted in enhanced sodium uptake and loss of the TsHKT1;2 intrinsic K(+) transporter activity. We consider the maintenance of K(+) uptake through TsHKT1;2 under salt stress an important component supporting the halophytic lifestyle of T. salsuginea.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Arabidopsis / drug effects
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Arabidopsis / genetics
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Arabidopsis / physiology
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Biological Transport
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Brassicaceae / drug effects
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Brassicaceae / genetics
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Brassicaceae / physiology*
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Cation Transport Proteins / genetics
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Cation Transport Proteins / metabolism*
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Evolution, Molecular
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Gene Expression Regulation, Plant
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Genes, Plant
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Homeostasis
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Molecular Sequence Data
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Mutagenesis, Site-Directed
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Phylogeny
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Plant Roots / genetics
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Plant Roots / physiology
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Plants, Genetically Modified / drug effects
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Plants, Genetically Modified / genetics
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Plants, Genetically Modified / physiology
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Potassium / metabolism*
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RNA Interference
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism
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Salt-Tolerant Plants / drug effects
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Salt-Tolerant Plants / genetics
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Salt-Tolerant Plants / physiology
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Sodium / metabolism
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Sodium Chloride / pharmacology*
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Species Specificity
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Substrate Specificity
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Symporters / genetics
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Symporters / metabolism*
Substances
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Arabidopsis Proteins
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Cation Transport Proteins
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HKT1 protein, Arabidopsis
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Symporters
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Sodium Chloride
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Sodium
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Potassium