Abstract
An important trait associated with the salt tolerance of wheat is the exclusion of sodium ions (Na+) from the shoot. We have previously shown that the sodium transporters TmHKT1;5-A and TaHKT1;5-D, from Triticum monoccocum (Tm) and Triticum aestivum (Ta), are encoded by genes underlying the major shoot Na+-exclusion loci Nax1 and Kna1, respectively. Here, using heterologous expression, we show that the affinity (K m) for the Na+ transport of TmHKT1;5-A, at 2.66 mM, is higher than that of TaHKT1;5-D at 7.50 mM. Through 3D structural modelling, we identify residues D471/a gap and D474/G473 that contribute to this property. We identify four additional mutations in amino acid residues that inhibit the transport activity of TmHKT1;5-A, which are predicted to be the result of an occlusion of the pore. We propose that the underlying transport properties of TmHKT1;5-A and TaHKT1;5-D contribute to their unique ability to improve Na+ exclusion in wheat that leads to an improved salinity tolerance in the field.
Keywords:
Bread; Einkorn; Gatekeeper cells; High-affinity K+ transporter; Ion transport; Mutagenesis; Salt exclusion; Salt tolerance; Structure–function; Xenopus; Yeast.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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Amino Acid Substitution
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Animals
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Binding Sites
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Cation Transport Proteins / chemistry*
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Cation Transport Proteins / genetics
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Cation Transport Proteins / metabolism
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Cloning, Molecular
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Gene Expression Regulation, Plant*
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Ion Transport
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Kinetics
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Models, Molecular
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Plant Proteins / chemistry*
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Plant Proteins / genetics
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Plant Proteins / metabolism
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Plant Shoots / genetics
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Plant Shoots / metabolism*
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Protein Binding
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Protein Interaction Domains and Motifs
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Protein Isoforms / chemistry
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Protein Isoforms / genetics
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Protein Isoforms / metabolism
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Protein Structure, Secondary
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism
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Salt Tolerance / genetics*
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Sodium / metabolism*
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Structure-Activity Relationship
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Symporters / chemistry*
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Symporters / genetics
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Symporters / metabolism
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Thermodynamics
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Triticum / genetics
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Triticum / metabolism*
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Xenopus laevis / genetics
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Xenopus laevis / metabolism
Substances
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Cation Transport Proteins
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HKT1 protein, plant
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Plant Proteins
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Protein Isoforms
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Recombinant Proteins
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Symporters
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Sodium