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.
Similar content being viewed by others
References
Schachtman DP, Schroeder JI (1994) Structure and transport mechanism of a high-affinity potassium uptake transporter from higher plants. Nature 370:655–658
Epstein E (1966) Dual pattern of ion absorption by plant cells and by plants. Nature 212:1324–1327
Platten JD, Cotsaftis O, Berthomieu P, Bohnert H, Davenport RJ, Fairbairn DJ, Horie T, Leigh RA, Lin H-X, Luan S (2006) Nomenclature for HKT transporters, key determinants of plant salinity tolerance. Trends Plant Sci 11(8):372–374
Rubio F, Gassmann W, Schroeder JI (1995) Sodium-driven potassium uptake by the plant potassium transporter HKT1 and mutations conferring salt tolerance. Science 270(5242):1660–1663
Gierth M, Mäser P (2007) Potassium transporters in plants–involvement in K+ acquisition, redistribution and homeostasis. FEBS Lett 581(12):2348–2356
Horie T, Hauser F, Schroeder JI (2009) HKT transporter-mediated salinity resistance mechanisms in Arabidopsis and monocot crop plants. Trends Plant Sci 14(12):660–668
Laurie S, Feeney KA, Maathuis FJ, Heard PJ, Brown SJ, Leigh RA (2002) A role for HKT1 in sodium uptake by wheat roots. Plant J 32(2):139–149
James RA, Davenport RJ, Munns R (2006) Physiological characterization of two genes for Na+ exclusion in durum wheat, Nax1 and Nax2. Plant Physiol 142(4):1537–1547
Läuchli A, James RA, Huang CX, McClluy M, Munns R (2008) Cell-specific localization of Na+ in roots of durum wheat and possible control points for salt exclusion. Plant Cell Environ 31(11):1565–1574
Sentenac H, Bonneaud N (1992) Cloning and expression in yeast of a plant potassium ion transport system. Science 256(5057):663–665
Corratgé-Faillie C, Jabnoune M, Zimmermann S, Véry A-A, Fizames C, Sentenac H (2010) Potassium and sodium transport in non-animal cells: the Trk/Ktr/HKT transporter family. Cell Mol Life Sci 67(15):2511–2532
Huang CS, Pedersen BP, Stokes DL (2017) Crystal structure of the potassium-importing KdpFABC membrane complex. Nature 546(7660):681–685
Mäser P, Hosoo Y, Goshima S, Horie T, Eckelman B, Yamada K, Yoshida K, Bakker EP, Shinmyo A, Oiki S (2002) Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants. Proc Natl Acad Sci USA 99(9):6428–6433
Cotsaftis O, Plett D, Shirley N, Tester M, Hrmova M (2012) A two-staged model of Na+ exclusion in rice explained by 3D modeling of HKT transporters and alternative splicing. PLoS One 7(7):e39865
Waters S, Gilliham M, Hrmova M (2013) Plant high-affinity potassium (HKT) transporters involved in salinity tolerance: structural insights to probe differences in ion selectivity. Int J Mol Sci 14(4):7660–7680
Singh A, Bhushan B, Gaikwad K, Yadav OP, Kumar S, Rai RD (2015) Induced defence responses of contrasting bread wheat genotypes under differential salt stress imposition. Indian J Biochem Biophys 52(1):75–85
Asins MJ, Villalta I, Aly MM, Olias R, Álvarez De Morales P, Huertas R, Li J, Jaime-Pérez N, Haro R, Raga V (2013) Two closely linked tomato HKT coding genes are positional candidates for the major tomato QTL involved in Na+/K+ homeostasis. Plant Cell Environ 36(6):1171–1191
Uozumi N, Kim EJ, Rubio F, Yamaguchi T, Muto S, Tsuboi A, Bakker EP, Nakamura T, Schroeder JI (2000) The Arabidopsis HKT1 gene homolog mediates inward Na+ currents in Xenopus laevis oocytes and Na+ uptake in Saccharomyces cerevisiae. Plant Physiol 122(4):1249–1260
Ren ZH, Gao JP, Li LG, Cai XL, Huang W, Chao DY, Zhu MZ, Wang ZY, Luan S, Lin HX (2005) A rice quantitative trait locus for salt tolerance encodes a sodium transporter. Nat Genet 37(10):1141–1146
Negrão S, Cecília Almadanim M, Pires IS, Abreu IA, Maroco J, Courtois B, Gregorio GB, McNally KL, Margarida Oliveira M (2013) New allelic variants found in key rice salt-tolerance genes: an association study. Plant Biotech J 11(1):87–100
Ariyarathna HCK, Ul-Haq T, Colmer TD, Francki MG (2014) Characterization of the multigene family TaHKT 2;1 in bread wheat and the role of gene members in plant Na+ and K+ status. BMC Plant Biol 14(1):1
Mishra S, Singh B, Panda K, Singh BP, Singh N, Misra P, Rai V, Singh NK (2016) Association of SNP haplotypes of HKT family genes with salt tolerance in indian wild rice germplasm. Rice 9(1):1
Kumar S, Beena A, Awana M, Singh A (2017) Physiological, biochemical, epigenetic and molecular analyses of wheat (Triticum aestivum) genotypes with contrasting salt tolerance. Front Plant Sci 8:1151
Diatloff E, Kumar R, Schachtman DP (1998) Site directed mutagenesis reduces the Na+ affinity of HKT1, an Na+ energized high affinity K+ transporter. FEBS Lett 432(1–2):31–36
Böhm J, Scherzer S, Shabala S, Krol E, Neher E, Mueller T, Hedrich R (2016) Venus flytrap HKT1-type channel provides for prey sodium uptake into carnivorous plant without conflicting with electrical excitability. Mol Plant 9(3):428–436
Almeida P, Katschnig D, de Boer AH (2013) HKT transporters-state of the art. Int J Mol Sci 14(10):20359–20385
Almeida P, de Boer G-J, de Boer AH (2014) Differences in shoot Na+ accumulation between two tomato species are due to differences in ion affinity of HKT1;2. J Plant Physiol 171(6):438–447
Ali A, Raddatz N, Aman R, Kim S, Park HC, Jan M, Baek D, Khan IU, Oh D-H, Lee SY (2016) A single amino acid substitution in the sodium transporter HKT1 associated with plant salt tolerance. Plant Physiol 171:2112–2126
Cao Y, Jin X, Huang H, Derebe MG, Levin EJ, Kabaleeswaran V, Pan Y, Punta M, Love J, Weng J (2011) Crystal structure of a potassium ion transporter, TrkH. Nature 471(7338):336–340
Mian A, Oomen RJ, Isayenkov S, Sentenac H, Maathuis FJ, Véry AA (2011) Over-expression of an Na+- and K+-permeable HKT transporter in barley improves salt tolerance. Plant J 68(3):468–479
Jabnoune M, Espeout S, Mieulet D, Fizames C, Verdeil J-L, Conéjéro G, Rodríguez-Navarro A, Sentenac H, Guiderdoni E, Abdelly C (2009) Diversity in expression patterns and functional properties in the rice HKT transporter family. Plant Physiol 150(4):1955–1971
Amar SB, Brini F, Sentenac H, Masmoudi K, Véry A-A (2014) Functional characterization in Xenopus oocytes of Na+ transport systems from durum wheat reveals diversity among two HKT1;4 transporters. J Exp Bot 65(1):213–222
Munns R, James RA, Xu B, Athman A, Conn SJ, Jordans C, Byrt CS, Hare RA, Tyerman SD, Tester M, Plett D, Gilliham M (2012) Wheat grain yield on saline soils is improved by an ancestral Na+ transporter gene. Nat Biotech 30(4):360–364
Byrt CS, Xu B, Krishnan M, Lightfoot DJ, Athman A, Jacobs AK, Watson-Haigh NS, Plett D, Munns R, Tester M (2014) The Na+ transporter, TaHKT1;5-D, limits shoot Na+ accumulation in bread wheat. Plant J 80(3):516–526
Tounsi S, Amar SB, Masmoudi K, Sentenac H, Brini F, Véry A-A (2016) Characterization of two HKT1;4 transporters from Triticum monococcum to elucidate the determinants of the wheat salt tolerance Nax1 QTL. Plant Cell Physiol 57(10):2047–2057
Baxter I, Brazelton JN, Yu D, Huang YS, Lahner B, Yakubova E, Li Y, Bergelson J, Borevitz JO, Nordborg M (2010) A coastal cline in sodium accumulation in Arabidopsis thaliana is driven by natural variation of the sodium transporter AtHKT1; 1. PLoS Genet 6(11):e1001193
Møller IS, Gilliham M, Jha D, Mayo GM, Roy SJ, Coates JC, Haseloff J, Tester M (2009) Shoot Na+ exclusion and increased salinity tolerance engineered by cell type-specific alteration of Na+ transport in Arabidopsis. Plant Cell 21(7):2163–2178
Plett D, Safwat G, Gilliham M, Møller IS, Roy S, Shirley N, Jacobs A, Johnson A, Tester M (2010) Improved salinity tolerance of rice through cell type-specific expression of AtHKT1; 1. PLoS One 5(9):e12571
Munns R, Gilliham M (2015) Salinity tolerance of crops–what is the cost? New Phytol 208(3):668–673
Ismail AM, Horie T (2017) Genomics, physiology, and molecular breeding approaches for improving salt tolerance. Annu Rev Plant Biol 68:405–434
Byrt CS, Platten JD, Spielmeyer W, James RA, Lagudah ES, Dennis ES, Tester M, Munns R (2007) HKT1; 5-like cation transporters linked to Na+ exclusion loci in wheat, Nax2 and Kna1. Plant Physiol 143(4):1918–1928
Vieira-Pires RS, Szollosi A, Morais-Cabral JH (2013) The structure of the KtrAB potassium transporter. Nature 496(7445):323–328
Fairbairn DJ, Liu W, Schachtman DP, Gomez-Gallego S, Day SR, Teasdale RD (2000) Characterisation of two distinct HKT1-like potassium transporters from Eucalyptus camaldulensis. Plant Mol Biol 43(4):515–525
Liu W, Fairbairn DJ, Reid RJ, Schachtman DP (2001) Characterization of two HKT1 homologues from Eucalyptus camaldulensis that display intrinsic osmosensing capability. Plant Physiol 127(1):283–294
Rodríguez-Navarro A, Ramos J (1984) Dual system for potassium transport in Saccharomyces cerevisiae. J Bacteriol 159(3):940–945
Laskowski RA, MacArthur MW, Moss DS, Thornton JM (1993) PROCHECK: a program to check the stereochemical quality of protein structures. J Appl Crystallogr 26(2):283–291
Sippl MJ (1993) Recognition of errors in three-dimensional structures of proteins. Proteins 17(4):355–362
Gille C, Birgit W, Gille A (2013) Sequence alignment visualization in HTML5 without Java. Bioinformatics 30(1):121–122
Edgar RC (2004) MUSCLE: multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Res 32(5):1792–1797
My Shen, Sali A (2006) Statistical potential for assessment and prediction of protein structures. Protein Sci 15(11):2507–2524
Landau M, Mayrose I, Rosenberg Y, Glaser F, Martz E, Pupko T, Ben-Tal N (2005) ConSurf 2005: the projection of evolutionary conservation scores of residues on protein structures. Nucleic Acids Res 33(suppl 2):W299–W302
Celniker G, Nimrod G, Ashkenazy H, Glaser F, Martz E, Mayrose I, Pupko T, Ben-Tal N (2013) ConSurf: using evolutionary data to raise testable hypotheses about protein function. Isr J Chem 53(3–4):199–206
James RA, Blake C, Byrt CS, Munns R (2011) Major genes for Na+ exclusion, Nax1 and Nax2 (wheat HKT1;4 and HKT1;5), decrease Na+ accumulation in bread wheat leaves under saline and waterlogged conditions. J Exp Bot 62(8):2939–2947
Henderson SW, Gilliham M (2015) The “Gatekeeper” concept: cell-type specific molecular mechanisms of plant adaptation to abiotic stress. In: Laitinen RAE (ed) Molecular mechanisms in plant adaptation. Wiley, New Jersey, pp 83–115
Byrt CS (2008) PhD thesis: Genes for sodium exclusion in wheat. University of Adelaide, Adelaide
Kelley LA, Sternberg MJ (2009) Protein structure prediction on the Web: a case study using the Phyre server. Nat Protoc 4(3):363–371
Zhang Y (2008) I-TASSER server for protein 3D structure prediction. BMC Bioinform 9(1):1
Wu S, Zhang Y (2007) LOMETS: a local meta-threading-server for protein structure prediction. Nucleic Acids Res 35(10):3375–3382
Pei J, Kim BH, Grishin NV (2008) PROMALS3D: a tool for multiple protein sequence and structure alignments. Nucleic Acids Res 36(7):2295–2300
Sali A, Blundell T (1993) Comparative protein modelling by satisfaction of spatial restraints. J Mol Biol 234(3):779–815
Author information
Authors and Affiliations
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.
Corresponding authors
Ethics declarations
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.).
Electronic supplementary material
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Xu, B., Waters, S., Byrt, C.S. et al. Structural variations in wheat HKT1;5 underpin differences in Na+ transport capacity. Cell. Mol. Life Sci. 75, 1133–1144 (2018). https://doi.org/10.1007/s00018-017-2716-5
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00018-017-2716-5