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Type: Journal article
Title: Structural variations in wheat HKT1;5 underpin differences in Na+ transport capacity
Author: Xu, B.
Waters, S.
Byrt, C.
Plett, D.
Tyerman, S.
Tester, M.
Munns, R.
Hrmova, M.
Gilliham, M.
Citation: Cellular and Molecular Life Sciences, 2018; 75(6):1133-1144
Publisher: Springer
Issue Date: 2018
ISSN: 1420-682X
Statement of
Bo Xu, Shane Waters, Caitlin S. Byrt, Darren Plett, Stephen D. Tyerman, Mark Tester, Rana Munns, Maria Hrmova, Matthew Gilliham
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 (Km) 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: Gatekeeper cells; salt exclusion; ion transport; structure-function; einkorn; bread; salt tolerance; Xenopus; mutagenesis; yeast; high-affinity K⁺ transporter
Rights: © Springer International Publishing AG, part of Springer Nature 2017
DOI: 10.1007/s00018-017-2716-5
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