Cellular and Molecular Life Sciences

, Volume 75, Issue 6, pp 1133–1144 | Cite as

Structural variations in wheat HKT1;5 underpin differences in Na+ transport capacity

  • Bo Xu
  • Shane Waters
  • Caitlin S. Byrt
  • Darren Plett
  • Stephen D. Tyerman
  • Mark Tester
  • Rana Munns
  • Maria Hrmova
  • Matthew Gilliham
Original Article

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

Gatekeeper cells Salt exclusion Ion transport Structure–function Einkorn Bread Salt tolerance Xenopus Mutagenesis Yeast High-affinity K+ transporter 

Notes

Author contributions

BX, MH, DP, and MG conceived the project out of work initiated by RM and MT. BX performed all experiments except the structural modelling and predictions (SW) and the cloning and original characterisation of TmHKT1;5-AK118E/L339P/Y379M (CSB). SDT advised on electrophysiology and analysis. MG, MH, and DP supervised the work. BX, SW, CSB, MH, and MG wrote the paper. All authors provided comment.

Compliance with ethical standards

Funding

This work was supported by the Grains Research and Development Corporation (UA00145, M.G.), the University of Adelaide Australian Postgraduate Award and the CJ Everald postgraduate scholarship (S.W.), and the Australian Research Council through the following schemes: Discovery (DP120100900, M.H.), Centre of Excellence (CE140100008, M.G., R.M., S.D.T), Future Fellowship (FT130100709, M.G.), and DECRA (DE150100837, C.S.B.).

Supplementary material

18_2017_2716_MOESM1_ESM.pdf (2 mb)
Supplementary material 1 (PDF 2024 kb)

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Copyright information

© Springer International Publishing AG, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research PrecinctUniversity of AdelaideGlen OsmondAustralia
  2. 2.School of Agriculture, Food and Wine, and Waite Research Institute, Waite Research PrecinctUniversity of AdelaideGlen OsmondAustralia
  3. 3.Division of Biological and Environmental Sciences and Engineering, Center for Desert AgricultureKing Abdullah University of Science and TechnologyThuwalKingdom of Saudi Arabia
  4. 4.School of Agriculture and Environment, and ARC Centre of Excellence in Plant Energy BiologyUniversity of Western AustraliaCrawleyAustralia

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