scholarly journals High affinity Na+ transport by wheat HKT1;5 is blocked by K+

2018 ◽  
Author(s):  
Bo Xu ◽  
Maria Hrmova ◽  
Matthew Gilliham
Keyword(s):  
Triticum Aestivum ◽  
Salt Tolerance ◽  
Heterologous Expression ◽  
Molecular Level ◽  
Structural Modelling ◽  
Na Transport ◽  
Sodium Transporters ◽  
High Affinity ◽  
Plant Salt Tolerance ◽  
External K

AbstractThe wheat sodium transporters TmHKT1;5-A and TaHKT1;5-D are encoded by genes underlying major shoot Na+ exclusion loci Nax2 and Kna1 from Triticum monococcum (Tm) and Triticum aestivum (Ta), respectively. In contrast to HKT2 transporters that have been shown to exhibit high affinity K+-dependent Na+ transport, HKT1 proteins have, with one exception, only been shown to catalyse low affinity Na+ transport and no K+ transport. Here, using heterologous expression in Xenopus laevis oocytes we show that both TmHKT1;5-A and TaHKT1;5-D encode dual (high and low) affinity Na+-transporters with the high-affinity component being abolished when external K+ is in excess of external Na+. Based on 3-D structural modelling we propose that tighter binding of K+, compared to that of Na+ in the selectivity filter region by means of additional van der Waals forces, explains the K+ block at the molecular level. The low-affinity component for Na+ transport of TmHKT1;5-A had a lower Km than that of TaHKT1;5-D and was less sensitive to external K+. We propose that these properties underpin the improvements in shoot Na+-exclusion and crop plant salt tolerance following the introgression of TmHKT1;5-A into diverse wheat backgrounds.

scholarly journals Soil Bacteria Confer Plant Salt Tolerance by Tissue-Specific Regulation of the Sodium Transporter HKT1

2008 ◽  
Vol 21 (6) ◽  
pp. 737-744 ◽  
Author(s):  
Huiming Zhang ◽  
Mi-Seong Kim ◽  
Yan Sun ◽  
Scot E. Dowd ◽  
Huazhong Shi ◽  
...  
Keyword(s):  
Salt Tolerance ◽  
Soil Bacteria ◽  
Tissue Specific ◽  
High Affinity ◽  
Bacterium Bacillus Subtilis ◽  
Microbe Interactions ◽  
Specific Regulation ◽  
Sodium Transporter ◽  
Bacterium Bacillus ◽  
Plant Salt Tolerance

Elevated sodium (Na+) decreases plant growth and, thereby, agricultural productivity. The ion transporter high-affinity K+ transporter (HKT)1 controls Na+ import in roots, yet dysfunction or overexpression of HKT1 fails to increase salt tolerance, raising questions as to HKT1's role in regulating Na+ homeostasis. Here, we report that tissue-specific regulation of HKT1 by the soil bacterium Bacillus subtilis GB03 confers salt tolerance in Arabidopsis thaliana. Under salt stress (100 mM NaCl), GB03 concurrently down- and upregulates HKT1 expression in roots and shoots, respectively, resulting in lower Na+ accumulation throughout the plant compared with controls. Consistent with HKT1 participation in GB03-induced salt tolerance, GB03 fails to rescue salt-stressed athkt1 mutants from stunted foliar growth and elevated total Na+ whereas salt-stressed Na+ export mutants sos3 show GB03-induced salt tolerance with enhanced shoot and root growth as well as reduced total Na+. These results demonstrate that tissue-specific regulation of HKT1 is critical for managing Na+ homeostasis in salt-stressed plants, as well as underscore the breadth and sophistication of plant–microbe interactions.

scholarly journals Downregulation of high-affinity potassium and sodium symporter gene, EcHKT1;1, in Eucalyptus roots enhances salt tolerance

2021 ◽  
Author(s):  
BALASUBRAMANIAN Aiyar ◽  
Selvakesavan Rajendran kamalabai ◽  
Shamili Krishnaraj ◽  
Sandhya M C ◽  
Usha Jayachandran ◽  
...  
Keyword(s):  
Salt Tolerance ◽  
Tree Species ◽  
External Medium ◽  
Major Gene ◽  
In Planta ◽  
Na Transport ◽  
High Affinity ◽  
Na Uptake ◽  
Transgenic Plantlets

Engineering for restricted root Na+ uptake could potentially enhance salt tolerance in Eucalyptus. High-affinity K+ transporters (HKTs) have been implicated in Na+ uptake from the external medium as in the case of TaHKT2;1 or in the unloading of Na+ from xylem like in AtHKT1;1. To rapidly determine the in planta role of EcHKT1:1, composite transgenics in which EcHKT1:1 was specifically downregulated via RNAi in the roots were generated. Compared to the controls that failed to survive at 350 mM NaCl, 33 % of the composite transgenic plantlets generated using the EcHKT1;1 silencing construct were able to tolerate up to 400 mM NaCl. In these composite transgenics, EcHKT1;1 downregulation ranged from 37 % to 74 %. The average shoot to root ratio of sodium was 4.9 folds lower than the controls indicating restricted translocation of Na+ to the shoots. Relative expression analysis in the leaves of two non-transgenic genotypes contrasting for their salt tolerance also showed downregulated EcHKT1;1 expression in the tolerant clone. The study thus determined that EcHKT1;1 is a major gene determining Na+ transport from the roots to shoots. This study also demonstrated the utility of the composite transgenic approach for screening genes conferring salt tolerance in tree species.

scholarly journals Na+ Transporter SvHKT1;1 from a Halophytic Turf Grass Is Specifically Upregulated by High Na+ Concentration and Regulates Shoot Na+ Concentration

2020 ◽  
Vol 21 (17) ◽  
pp. 6100
Author(s):  
Yuki Kawakami ◽  
Shahin Imran ◽  
Maki Katsuhara ◽  
Yuichi Tada
Keyword(s):  
Salt Stress ◽  
Salt Tolerance ◽  
Early Stage ◽  
Constitutive Expression ◽  
Xenopus Laevis Oocytes ◽  
Na Transport ◽  
Turf Grass ◽  
Defective Mutant ◽  
Reduced Salt ◽  
Na Uptake

We characterized an Na+ transporter SvHKT1;1 from a halophytic turf grass, Sporobolus virginicus. SvHKT1;1 mediated inward and outward Na+ transport in Xenopus laevis oocytes and did not complement K+ transporter-defective mutant yeast. SvHKT1;1 did not complement athkt1;1 mutant Arabidopsis, suggesting its distinguishable function from other typical HKT1 transporters. The transcript was abundant in the shoots compared with the roots in S. virginicus and was upregulated by severe salt stress (500 mM NaCl), but not by lower stress. SvHKT1;1-expressing Arabidopsis lines showed higher shoot Na+ concentrations and lower salt tolerance than wild type (WT) plants under nonstress and salt stress conditions and showed higher Na+ uptake rate in roots at the early stage of salt treatment. These results suggested that constitutive expression of SvHKT1;1 enhanced Na+ uptake in root epidermal cells, followed by increased Na+ transport to shoots, which led to reduced salt tolerance. However, Na+ concentrations in phloem sap of the SvHKT1;1 lines were higher than those in WT plants under salt stress. Based on this result, together with the induction of the SvHKT1;1 transcription under high salinity stress, it was suggested that SvHKT1;1 plays a role in preventing excess shoot Na+ accumulation in S. virginicus.

Hexaconazole–Cu complex improves the salt tolerance of Triticum aestivum seedlings

2016 ◽  
Vol 127 ◽  
pp. 90-94 ◽  
Author(s):  
Jie Li ◽  
Cuiyu Sun ◽  
Nan Yu ◽  
Chen Wang ◽  
Tongtong Zhang ◽  
...  
Keyword(s):  
Triticum Aestivum ◽  
Salt Tolerance ◽  
Cu Complex

A Functional Alternative Oxidase Modulates Plant Salt Tolerance in Physcomitrella patens

2019 ◽  
Vol 60 (8) ◽  
pp. 1829-1841 ◽  
Author(s):  
Guochun Wu ◽  
Sha Li ◽  
Xiaochuan Li ◽  
Yunhong Liu ◽  
Shuangshuang Zhao ◽  
...  
Keyword(s):  
Salt Stress ◽  
Salt Tolerance ◽  
Stress Responses ◽  
Alternative Oxidase ◽  
Physcomitrella Patens ◽  
Redox Homeostasis ◽  
Respiratory Pathway ◽  
Functional Link ◽  
Salt Stress Condition ◽  
Plant Salt Tolerance

Abstract Alternative oxidase (AOX) has been reported to be involved in mitochondrial function and redox homeostasis, thus playing an essential role in plant growth as well as stress responses. However, its biological functions in nonseed plants have not been well characterized. Here, we report that AOX participates in plant salt tolerance regulation in moss Physcomitrella patens (P. patens). AOX is highly conserved and localizes to mitochondria in P. patens. We observed that PpAOX rescued the impaired cyanide (CN)-resistant alternative (Alt) respiratory pathway in Arabidopsis thaliana (Arabidopsis) aox1a mutant. PpAOX transcription and Alt respiration were induced upon salt stress in P. patens. Using homologous recombination, we generated PpAOX-overexpressing lines (PpAOX OX). PpAOX OX plants exhibited higher Alt respiration and lower total reactive oxygen species accumulation under salt stress condition. Strikingly, we observed that PpAOX OX plants displayed decreased salt tolerance. Overexpression of PpAOX disturbed redox homeostasis in chloroplasts. Meanwhile, chloroplast structure was adversely affected in PpAOX OX plants in contrast to wild-type (WT) P. patens. We found that photosynthetic activity in PpAOX OX plants was also lower compared with that in WT. Together, our work revealed that AOX participates in plant salt tolerance in P. patens and there is a functional link between mitochondria and chloroplast under challenging conditions.

scholarly journals GPVI (Glycoprotein VI) Interaction With Fibrinogen Is Mediated by Avidity and the Fibrinogen αC-Region

2021 ◽  
Vol 41 (3) ◽  
pp. 1092-1104
Author(s):  
Rui-Gang Xu ◽  
Julia S. Gauer ◽  
Stephen R. Baker ◽  
Alexandre Slater ◽  
Eleyna M. Martin ◽  
...  
Keyword(s):  
Molecular Level ◽  
Dissociation Rate ◽  
Fibrin Polymerization ◽  
Downstream Signaling ◽  
Protein Protein Interaction ◽  
Glycoprotein Vi ◽  
High Affinity ◽  
Platelet Signaling ◽  
Dimeric Form ◽  
Affinity Interaction

Objective: GPVI (glycoprotein VI) is a key molecular player in collagen-induced platelet signaling and aggregation. Recent evidence indicates that it also plays important role in platelet aggregation and thrombus growth through interaction with fibrin(ogen). However, there are discrepancies in the literature regarding whether the monomeric or dimeric form of GPVI binds to fibrinogen at high affinity. The mechanisms of interaction are also not clear, including which region of fibrinogen is responsible for GPVI binding. We aimed to gain further understanding of the mechanisms of interaction at molecular level and to identify the regions on fibrinogen important for GPVI binding. Approach and Results: Using multiple surface- and solution-based protein-protein interaction methods, we observe that dimeric GPVI binds to fibrinogen with much higher affinity and has a slower dissociation rate constant than the monomer due to avidity effects. Moreover, our data show that the highest affinity interaction of GPVI is with the αC-region of fibrinogen. We further show that GPVI interacts with immobilized fibrinogen and fibrin variants at a similar level, including a nonpolymerizing fibrin variant, suggesting that GPVI binding is independent of fibrin polymerization. Conclusions: Based on the above findings, we conclude that the higher affinity of dimeric GPVI over the monomer for fibrinogen interaction is achieved by avidity. The αC-region of fibrinogen appears essential for GPVI binding. We propose that fibrin polymerization into fibers during coagulation will cluster GPVI through its αC-region, leading to downstream signaling, further activation of platelets, and potentially stimulating clot growth. Graphic Abstract: A graphic abstract is available for this article.

scholarly journals Improvement Salt Tolerance of Safflower Plants by Endophytic Bacteria

2019 ◽  
Vol 5 ◽  
pp. 38-56 ◽  
Author(s):  
Khulod A. Hemida ◽  
Amany M.M. Reyad
Keyword(s):  
Salt Tolerance ◽  
Plant Growth ◽  
Endophytic Bacteria ◽  
Bacterial Species ◽  
Limiting Factors ◽  
Symbiotic Association ◽  
Bacterial Strains ◽  
Growth Promoters ◽  
Wide Range ◽  
Plant Salt Tolerance

Salinity is one of the most dangerous environmental limiting factors of the plant productivity. A wide range of adaptation strategies is required to overcome salinity stress. However, such strategies seem to be long drawn and cost-intensive. It has been confirmed in recent years that plant growth promoting endophytes (PGPEs) that have the ability to further build a symbiotic association with their host to improve host plant salt tolerance. In our investigation try to improve plant salt tolerance using different species of endophytic bacteria. From the total eight endophytic bacterial species were isolated from root, stem, and leaf of Carthamustinctorius (safflower) plant, two isolates were capable of using 1-aminocyclopropane-1-carboxylic acid (ACC) as a sole nitrogen source, and they are of positive results for (ACC) deaminase activity and indole-3-acetic acid (IAA) production. The bacterial isolates were identified using 16S ribosomal DNA technique as Bacillus cereus and Bacillus aerius and had accession numbers MG708176 and MG711593 respectively, by submitting their sequences in GenBank database. This study showed that the bacterial strains B. cereus and B. aerius are valuable biological plant growth promoters that could enhance salt tolerance in Safflower plants under 100, 200, and 300mMNaCl levels resulting in an increase in plant growth and ascorbate-glutathione redox cycle, in comparison with the non-inoculated controls. Our findings reported that the co-inoculation of the two selected endophytic bacteria strains were successfully isolated from Safflower seedlings significantly alleviated the harmful effects of salt stress, promoted plant growth and biomass yield.

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