Functions of HKT transporters in sodium transport in roots and in protecting leaves from salinity stress

Horie, Tomoaki; Sugawara, Mitsuo; Okunou, K.; Nakayama, Hideki; Schroeder, Julian I.; Shinmyo, Atsuhiko; Yoshida, Kazuya

doi:10.5511/plantbiotechnology.25.233

Cited by 25 publications

(22 citation statements)

References 37 publications

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“…The HKT transporter has been found in many plant species. However, the regulatory mechanism is still not known (Horie et al, 2008). Understanding the mechanism of development of salt tolerant plants either by genetic engineering or use of plantgrowth-promoting bacteria is essential for solving the problem of productivity in salty regions (Dimkpa et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

The plant-growth-promoting bacterium Klebsiella sp. SBP-8 confers induced systemic tolerance in wheat (Triticum aestivum) under salt stress

Singh

Jha

2015

Journal of Plant Physiology

221

102

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Section: Introductionmentioning

confidence: 99%

The plant-growth-promoting bacterium Klebsiella sp. SBP-8 confers induced systemic tolerance in wheat (Triticum aestivum) under salt stress

Singh

Jha

2015

Journal of Plant Physiology

221

102

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“…Multiple HKT genes are found in monocot genomes [28,29,49,53]. Studies of Arabidopsis plants carrying mutations in AtHKT1;1 revealed that Na + -selective transport via AtHKT1;1 has an essential role in Na + exclusion from leaves and K + homeostasis in leaves during salinity stress [11,24,26,27,54–56]. Here, we review findings of the functions of AtHKT1;1 and its orthologs in rice ( Oryza sativa ) and durum wheat ( Triticum turgidum durum ), which mediate a major salinity-resistant mechanism both in dicots and monocots via Na + exclusion from leaves.…”

mentioning

confidence: 99%

HKT transporter-mediated salinity resistance mechanisms in Arabidopsis and monocot crop plants

Horie

Hauser

Schroeder

2009

Trends in Plant Science

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436

352

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The salinization of irrigated lands is increasingly detrimental to plant biomass production and agricultural productivity as most plant species are sensitive to high concentrations of sodium (Na + ), which causes combined Na + toxicity and osmotic stress. Plants have multiple Na + transport systems to circumvent Na + toxicity. Essential physiological functions of major Na + transporters and their mechanisms mediating salinity resistance have been identified in Arabidopsis, including the SOS1, AtNHX and AtHKT1;1 transporters. As we discuss here, recent studies have demonstrated that a class of xylem-parenchyma-expressed Na + -permeable plant HKT transporters represent a primary mechanism mediating salt tolerance and Na + exclusion from leaves in Arabidopsis, and that major salt tolerance QTL in monocot crop plants are also based on this HKT-mediated mechanism. Sodium toxicity and salt tolerance in plants Physiological studies have shown that salinity stress in plants is multifactorial, including osmotic stress [1] and cellular sodium (Na + ) toxicity, such as inhibition of vital enzymes and metabolic processes [2][3][4][5][6][7][8][9][10][11][12][13][14]. Photosynthetic processes are among the most sensitive to salinity and, therefore, salinity stress directly reduces carbon fixation and biomass production in plants [5,[15][16][17][18]. Sodium transport processes have major roles in salinity tolerance, including organellar Na + sequestration [4,8,9,15,19,20]; Na + extrusion by plasma membrane Na + -H + exchange transporters, such as AtSOS1 [21,22] and exclusion of Na + from leaves and shoots [11,[23][24][25][26][27][28][29]. In addition, reducing Na + uptake or increasing cytoplasmic potassium (K + ) levels relative to Na + increases Na + tolerance in plants [30][31][32][33]. However, given that multiple independent cationic nutrient uptake transporters mediate Na + uptake from the soil into roots (reviewed in Refs [6,34]), engineering of reduced Na + influx into plant roots is likely a more challenging endeavor. The identification and characterization of Na + -permeable transporters is therefore pivotal to understanding plant Na + toxicity and tolerance [13,[35][36][37][38].Recent research has demonstrated that members of the high-affinity K + transporter (HKT) transporter/channel family mediate important Na + tolerance mechanisms in plants. The TaHKT2;1 gene from wheat (Triticum aestivum) (previously named HKT1), was the first HKT transporter gene found in plants [39]. It was shown to mediate high-affinity Na + -K + cotransport and also preferred Na + -selective low-affinity Na + transport in the presence of a Corresponding author: Horie, T. (horie@rib.okayama-u.ac.jp). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please ...

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“…permeability to this transporter. Site-directed mutagenesis of this signature glycine residue in TaHKT2;1 [6] and OsHKT2;2 [32] revealed the importance of these residues in K ? selectivity.…”

Section: Discussionmentioning

confidence: 98%

A Low-Affinity K+ Transporter AlHKT2;1 from Recretohalophyte Aeluropus lagopoides Confers Salt Tolerance in Yeast

et al. 2015

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The high-affinity potassium transporters (HKT) are highly important for stress tolerance in plants as they uniquely maintain K(+)/Na(+) ratio for their survival and growth. In this study a novel HKT gene AlHKT2;1 was isolated and characterized from salt secreting halophyte, Aeluropus lagopoides. The AlHKT2;1 cDNA comprised of an open reading frame of 1,581 bp, encoding a protein of 526 amino acid residues. It belongs to class II HKTs and showed high homology with other HKT genes. Functional characterization of AlHKT2;1 in both K(+) uptake-deficient (WΔ6) and Na(+)-sensitive yeast mutants (G19) showed the characteristic feature of low-affinity K(+) transporter supporting the growth at >1 mM KCl concentration. The transformed yeast cells showed high sensitivity to NaCl; however, the addition of KCl along with NaCl support the growth of AlHKT2;1 expressing mutant. Ion content analysis of yeast cells with AlHKT2;1 grown in high NaCl medium supplemented with KCl revealed that salt tolerance was correlated with accumulation of K(+) during salt stress. These results suggest that AlHKT2;1 plays an important role in the K(+) uptake during salt stress and in maintaining a high K(+)/Na(+) ratio in the cytosol.

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Functions of HKT transporters in sodium transport in roots and in protecting leaves from salinity stress

Cited by 25 publications

References 37 publications

The plant-growth-promoting bacterium Klebsiella sp. SBP-8 confers induced systemic tolerance in wheat (Triticum aestivum) under salt stress

The plant-growth-promoting bacterium Klebsiella sp. SBP-8 confers induced systemic tolerance in wheat (Triticum aestivum) under salt stress

HKT transporter-mediated salinity resistance mechanisms in Arabidopsis and monocot crop plants

A Low-Affinity K+ Transporter AlHKT2;1 from Recretohalophyte Aeluropus lagopoides Confers Salt Tolerance in Yeast

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