The Na(+) transporter, TaHKT1;5-D, limits shoot Na(+) accumulation in bread wheat.

Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K(+) /Na(+) ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na(+) -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na(+) concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na(+) from the xylem vessels in the root and has an important role in restricting the transport of Na(+) from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na(+) exclusion and is critical in maintaining a high K(+) /Na(+) ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes.

[1]  R. Burton,et al.  Protocol: a fast and simple in situ PCR method for localising gene expression in plant tissue , 2014, Plant Methods.

[2]  J. Batley,et al.  A chromosome-based draft sequence of the hexaploid bread wheat (Triticum aestivum) genome , 2014, Science.

[3]  H. Sentenac,et al.  Functional characterization in Xenopus oocytes of Na+ transport systems from durum wheat reveals diversity among two HKT1;4 transporters , 2013, Journal of experimental botany.

[4]  P. Hasegawa Sodium (Na+) homeostasis and salt tolerance of plants , 2013 .

[5]  Leon V. Kochian,et al.  Using membrane transporters to improve crops for sustainable food production , 2013, Nature.

[6]  M. Gilliham,et al.  Plant High-Affinity Potassium (HKT) Transporters Involved in Salinity Tolerance: Structural Insights to Probe Differences in Ion Selectivity , 2013, International journal of molecular sciences.

[7]  A. Verbyla,et al.  Assessing the importance of subsoil constraints to yield of wheat and its implications for yield improvement , 2013, Crop and Pasture Science.

[8]  Kenneth L. McNally,et al.  New allelic variants found in key rice salt-tolerance genes: an association study. , 2013, Plant biotechnology journal.

[9]  A. Ismail,et al.  Salinity tolerance, Na+ exclusion and allele mining of HKT1;5 in Oryza sativa and O. glaberrima: many sources, many genes, one mechanism? , 2013, BMC Plant Biology.

[10]  S. Conn,et al.  Protocol: optimising hydroponic growth systems for nutritional and physiological analysis of Arabidopsis thaliana and other plants , 2013, Plant Methods.

[11]  R. Munns,et al.  Impact of ancestral wheat sodium exclusion genes Nax1 and Nax2 on grain yield of durum wheat on saline soils. , 2012, Functional plant biology : FPB.

[12]  M. Tester,et al.  A Two-Staged Model of Na+ Exclusion in Rice Explained by 3D Modeling of HKT Transporters and Alternative Splicing , 2012, PloS one.

[13]  M. Tester,et al.  Wheat grain yield on saline soils is improved by an ancestral Na+ transporter gene , 2012, Nature Biotechnology.

[14]  R. Oomen,et al.  Over-expression of an Na+-and K+-permeable HKT transporter in barley improves salt tolerance. , 2011, The Plant journal : for cell and molecular biology.

[15]  R. Munns,et al.  Genetic mapping and marker development for resistance of wheat against the root lesion nematode Pratylenchus neglectus , 2013, BMC Plant Biology.

[16]  L. Sollid,et al.  Effective shutdown in the expression of celiac disease-related wheat gliadin T-cell epitopes by RNA interference , 2010, Proceedings of the National Academy of Sciences.

[17]  M. Tester,et al.  Improved Salinity Tolerance of Rice Through Cell Type-Specific Expression of AtHKT1;1 , 2010, PloS one.

[18]  F. Hauser,et al.  A conserved primary salt tolerance mechanism mediated by HKT transporters: a mechanism for sodium exclusion and maintenance of high K(+)/Na(+) ratio in leaves during salinity stress. , 2010, Plant, cell & environment.

[19]  P. Langridge,et al.  HvNax3—a locus controlling shoot sodium exclusion derived from wild barley (Hordeum vulgare ssp. spontaneum) , 2010, Functional & Integrative Genomics.

[20]  J. Schroeder,et al.  HKT transporter-mediated salinity resistance mechanisms in Arabidopsis and monocot crop plants. , 2009, Trends in plant science.

[21]  M. Tester,et al.  Shoot Na + Exclusion and Increased Salinity Tolerance Engineered by Cell Type–specific Alteration of Na + Transport in Arabidopsis Enhancer Trap Lines Driving Cell Type–specific Gene Expression in the Stelar Cells of the Mature Root , 2022 .

[22]  M. Tester,et al.  Investigating glutamate receptor-like gene co-expression in Arabidopsis thaliana. , 2008, Plant, cell & environment.

[23]  M. Tester,et al.  Mechanisms of salinity tolerance. , 2008, Annual review of plant biology.

[24]  R. Munns,et al.  Comparative mapping of HKT genes in wheat, barley, and rice, key determinants of Na+ transport, and salt tolerance. , 2008, Journal of experimental botany.

[25]  Klaus Palme,et al.  A cysteine-rich receptor-like kinase NCRK and a pathogen-induced protein kinase RBK1 are Rop GTPase interactors. , 2007, The Plant journal : for cell and molecular biology.

[26]  Caitlin S. Byrt Genes for sodium exclusion in wheat. , 2008 .

[27]  C. Offler,et al.  Aquaporins and unloading of phloem-imported water in coats of developing bean seeds. , 2007, Plant, cell & environment.

[28]  M. Tester,et al.  Reassessment of tissue Na(+) concentration as a criterion for salinity tolerance in bread wheat. , 2007, Plant, cell & environment.

[29]  J. Sheen,et al.  Arabidopsis mesophyll protoplasts: a versatile cell system for transient gene expression analysis , 2007, Nature Protocols.

[30]  J. Schroeder,et al.  Rice OsHKT2;1 transporter mediates large Na+ influx component into K+‐starved roots for growth , 2007, The EMBO journal.

[31]  M. Tester,et al.  HKT1;5-Like Cation Transporters Linked to Na+ Exclusion Loci in Wheat, Nax2 and Kna11[OA] , 2007, Plant Physiology.

[32]  R. Schiestl,et al.  High-efficiency yeast transformation using the LiAc/SS carrier DNA/PEG method , 2007, Nature Protocols.

[33]  R. Schiestl,et al.  Large-scale high-efficiency yeast transformation using the LiAc/SS carrier DNA/PEG method , 2007, Nature Protocols.

[34]  Guoying Wang,et al.  Genetic analysis of salt tolerance in a recombinant inbred population of wheat (Triticum aestivum L.) , 2006, Euphytica.

[35]  R. Munns,et al.  A Sodium Transporter (HKT7) Is a Candidate for Nax1, a Gene for Salt Tolerance in Durum Wheat1[W][OA] , 2006, Plant Physiology.

[36]  R. Munns,et al.  Physiological Characterization of Two Genes for Na+ Exclusion in Durum Wheat, Nax1 and Nax21 , 2006, Plant Physiology.

[37]  M. Tester,et al.  Nomenclature for HKT transporters, key determinants of plant salinity tolerance. , 2006, Trends in plant science.

[38]  P. Rengasamy World salinization with emphasis on Australia. , 2006, Journal of experimental botany.

[39]  J. Gorham,et al.  Partial characterization of the trait for enhanced K+−Na+ discrimination in the D genome of wheat , 1990, Planta.

[40]  M. Osumi,et al.  Enhanced salt tolerance mediated by AtHKT1 transporter-induced Na unloading from xylem vessels to xylem parenchyma cells. , 2005, The Plant journal : for cell and molecular biology.

[41]  S. Luan,et al.  A rice quantitative trait locus for salt tolerance encodes a sodium transporter , 2005, Nature Genetics.

[42]  P. Quail,et al.  Ubiquitin promoter-based vectors for high-level expression of selectable and/or screenable marker genes in monocotyledonous plants , 1996, Transgenic Research.

[43]  D. Pomp,et al.  Development of obesity following inactivation of a growth hormone transgene in mice , 2005, Transgenic Research.

[44]  R. Munns,et al.  A locus for sodium exclusion (Nax1), a trait for salt tolerance, mapped in durum wheat. , 2004, Functional plant biology : FPB.

[45]  D. Pimentel,et al.  Water Resources: Agricultural and Environmental Issues , 2004 .

[46]  Miftahudin,et al.  A Chromosome Bin Map of 16,000 Expressed Sequence Tag Loci and Distribution of Genes Among the Three Genomes of Polyploid Wheat , 2004, Genetics.

[47]  R. Burton,et al.  The CesA Gene Family of Barley. Quantitative Analysis of Transcripts Reveals Two Groups of Co-Expressed Genes1 , 2004, Plant Physiology.

[48]  J. Dvorak,et al.  Engineering of interstitial foreign chromosome segments containing the K+/Na+ selectivity gene Kna1 by sequential homoeologous recombination in durum wheat , 1996, Theoretical and Applied Genetics.

[49]  J. Dvorak,et al.  Mapping of the K+/Na+ discrimination locus Kna1 in wheat , 1996, Theoretical and Applied Genetics.

[50]  J. Dvorak,et al.  Enhancement of the salt tolerance of Triticum turgidum L. by the Kna1 locus transferred from the Triticum aestivum L. chromosome 4D by homoeologous recombination , 1994, Theoretical and Applied Genetics.

[51]  C. N. Law,et al.  Chromosomal location of a K/Na discrimination character in the D genome of wheat , 1987, Theoretical and Applied Genetics.

[52]  R. Munns,et al.  Genetic control of sodium exclusion in durum wheat , 2003 .

[53]  M. Sussman,et al.  Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKT1 , 2002, FEBS letters.

[54]  J. Schroeder,et al.  Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[55]  M. Warburton,et al.  Identification of highly transformable wheat genotypes for mass production of fertile transgenic plants. , 2002, Genome.

[56]  M. G. Pitman,et al.  Global Impact of Salinity and Agricultural Ecosystems , 2002 .

[57]  J. P. Gustafson,et al.  Genetic and physical characterization of chromosome 4DL in wheat. , 2001, Genome.

[58]  D. Byrne,et al.  Marker gene expression driven by the maize ubiquitin promoter in transgenic wheat , 2000 .

[59]  J. Schroeder,et al.  The Arabidopsis HKT1 gene homolog mediates inward Na(+) currents in xenopus laevis oocytes and Na(+) uptake in Saccharomyces cerevisiae. , 2000, Plant physiology.

[60]  R. Munns,et al.  Genetic variation for improving the salt tolerance of durum wheat , 2000 .

[61]  T. Kinouchi,et al.  [Sodium (Na)]. , 1999, Nihon rinsho. Japanese journal of clinical medicine.

[62]  J. Schroeder,et al.  Alkali cation selectivity of the wheat root high-affinity potassium transporter HKT1. , 1996, The Plant journal : for cell and molecular biology.

[63]  J. Dvorak,et al.  Methodology of gene transfer by homoeologous recombination into Triticum turgidum: transfer of K+/Na+ discrimination from Triticum aestivum , 1992 .

[64]  J. Ramos,et al.  Dual system for potassium transport in Saccharomyces cerevisiae , 1984, Journal of bacteriology.