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.

scholarly journals Polymerization of actin. IV. Role of Ca++ and H+ in the assembly of actin and in membrane fusion in the acrosomal reaction of echinoderm sperm

1978 ◽  
Vol 77 (2) ◽  
pp. 536-550 ◽  
Author(s):  
LG Tilney ◽  
DP Kiehart ◽  
C Sardet ◽  
M Tilney
Keyword(s):  
Cell Surface ◽  
Membrane Fusion ◽  
Intracellular Ph ◽  
Actin Filaments ◽  
External Medium ◽  
Ionophore A23187 ◽  
Natural Stimulus ◽  
High Affinity ◽  
Acrosomal Reaction

When Pisaster, Asterias, or Thyone sperm are treated with the ionophore A23187 or X537A, an acrosomal reaction similar but not identical to a normal acrosomal reaction is induced in all the sperm. Based upon the response of the sperm, the acrosomal reaction consists of a series of temporally related steps. These include the fusion of the acrosomal vacuole with the cell surface, the polymerization of the actin, the alignment of the actin filaments, an increase in volume, an increase in the limiting membrane, and changes in the shape of the nucleus. In this report, we have concentrated on the first two steps in this sequence. Although fusion of the acrosomal vacuole with the cell surface requires Ca++, we found that the polymerization of actin instead appears to be dependent upon an increase in intracellular pH. This conclusion was reached by applying to sperm A23187, X537A, or nigericin, ionophores which all carry H+ at high affinity, yet vary in their affinity for other cations. When sperm are suspended in isotonic NaCl, isotonic KCl, calcium-free seawater, or seawater, all at pH 8.0, and the ionophore is added, the actin polymerizes explosively and an efflux of H+ from the cell occurs. However, if the pH, of the external medium is maintained at 6.5, the presumed intracellular pH, no effect is observed. And, finally, if egg jelly is added to sperm (the natural stimulus for the acrosomal reaction) at pH 8.0, H+ is also released. On the basis of these observations and those presented in earlier papers in this series, we conclude that a rise in intracellular pH induces the actin to disassociate from its binding proteins. Now it can polymerize.

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 Effect of estrogen on calcium and sodium transport by the nephron luminal membranes

2001 ◽  
Vol 170 (2) ◽  
pp. 441-450 ◽  
Author(s):  
MG Brunette ◽  
M Leclerc
Keyword(s):  
Membrane Vesicles ◽  
Distal Tubule ◽  
Maximal Effect ◽  
Osteoporosis Prevention ◽  
Na Transport ◽  
High Affinity ◽  
Distal Tubules ◽  
Dose Dependent ◽  
Filtration Technique ◽  
Na Uptake

Estrogens are widely used for contraception and osteoporosis prevention. The aim of the present study was to investigate the effect of 17 beta-estradiol on calcium (Ca(2+)) transport by the nephron luminal membranes, independently of any other Ca(2+)-regulating hormones. Proximal and distal tubules of rabbit kidneys were incubated with 17 beta-estradiol or the carrier for various periods of time, and the luminal membranes of these tubules were purified and vesiculated. Ca(2+) uptake by membrane vesicles was measured using the Millipore filtration technique. Incubation of proximal tubules with the hormone did not influence Ca(2+) uptake by the luminal membranes. In contrast, incubation of distal tubules with 10(-8) M 17 beta-estradiol for 30 min decreased the initial uptake of 0.5 mM Ca(2+) from 0.34+/-0.04 (s.e.m. ) to 0.17+/-0.04 pmol/microg per 5 s (P<0.05). In the presence of 100 mM Na(+), 0.5 mM Ca(2+) uptake was strongly diminished and the effect of 17 beta-estradiol disappeared (0.17+/-0.01 and 0.21+/-0.07 pmol/microg per 5 s in vesicles from the control and treated tubules). Direct incubation of the membranes with 17 beta-estradiol, however, failed to show any influence of the hormone on Ca(2+) transport. The action of 17 beta-estradiol was dose-dependent, with a half-maximal effect at approximately 10(-9) M. Ca(2+) uptake by the distal tubule membranes presents dual kinetics. 17 beta-Estradiol decreased the V(max) value of the high-affinity component from 0.42+/-0.02 to 0.31+/-0.03 pmol/microg per 10 s (P<0.02). In contrast with the effect of the hormone on Ca(2+) transport, estradiol increased Na(+) uptake by both the proximal and distal tubule luminal membranes. In conclusion, incubation of proximal and distal tubules with estrogen decreases Ca(2+) reabsorption by the high-affinity Ca(2+) channels of the distal luminal membranes, and enhances Na(+) transport by the membranes from proximal and distal nephrons.

Na+ transport properties of isolated rat parotid acini

1990 ◽  
Vol 259 (6) ◽  
pp. G1044-G1055 ◽  
Author(s):  
S. Dissing ◽  
B. Nauntofte
Keyword(s):  
Transport Properties ◽  
Na Transport ◽  
Cell Water ◽  
Exchange System ◽  
Physiological Conditions ◽  
Cotransport System ◽  
Rat Parotid ◽  
The Relationship ◽  
Na Uptake

The effect of carbachol stimulation on the Na+ transport properties of rat parotid acini was characterized. Upon stimulation, the acinar Na+ concentration increased from 20 to 70 mM within 25 s, whereafter a backregulation toward the prestimulatory level was observed, mediated by the Na(+)-K+ pump. The transport mechanisms responsible for the net Na+ uptake observed between 10 and 20 s after carbachol stimulation in a Krebs-Ringer-bicarbonate medium (KRB) consisted of a dimethylamiloride-sensitive Na(+)-H+ exchange system (3.5 mmol.liter cell water-1.s-1 or approximately 75% of the total Na+ influx) and a bumetanide-sensitive cotransport system (of approximately 15%). The data are consistent with the residual influx being mediated by amiloride-sensitive Na+ channels. In unstimulated acini acidified by a NH4+ prepulse technique, the relationship between intracellular pH (pHi) and the rate of acinar Na(+)-H+ exchange was determined. At pHi 6.5 the rate of Na(+)-H+ exchange in a KRB medium amounted to 1.2 mmol.liter cell water-1.s-1 and ceased when pHi had recovered to 7.2. It was concluded that under physiological conditions carbachol stimulation activates Na(+)-H+ exchange, an effect that is responsible for the major part of the Na+ gain after stimulation. The role of cotransport in mediating net Cl- uptake against an electrochemical gradient was investigated. It was found that when the Na+ gradient is strongly reduced (in a 20 mM Na+ medium) a Cl(-)-HCO3- exchange system can mediate a net Cl- uptake at a rate similar to the rate observed in a medium containing high Na+. The results are compatible with both Cl(-)-HCO3- exchange and cotransport keeping an intracellular Cl- concentration above the electrochemical equilibrium under physiological conditions.

Neuronal and Extraneuronal Uptake of 3H-Norepinephrine in the Heart of the Active Bat: An Electron Microscopic Radioautographic Study

1973 ◽  
Vol 31 ◽  
pp. 522-523
Author(s):  
Martin Hagopian ◽  
Michael D. Gershon ◽  
Eladio A. Nunez
Keyword(s):  
Smooth Muscle ◽  
Monoamine Oxidase ◽  
Vascular Smooth Muscle ◽  
Cardiac Muscle ◽  
Maximum Rate ◽  
External Medium ◽  
Extraneuronal Uptake ◽  
Electron Microscopic ◽  
Cardiac Tissues ◽  
High Affinity

The ability of cardiac tissues to take up norepinephrine from an external medium is well known. Two mechanisms, called Uptake and Uptake respectively by Iversen have been differentiated. Uptake is a high affinity system associated with adrenergic neuronal elements. Uptake is a low affinity system, with a higher maximum rate than that of Uptake. Uptake has been associated with extraneuronal tissues such as cardiac muscle, fibroblasts or vascular smooth muscle. At low perfusion concentrations of norepinephrine most of the amine taken up by Uptake is metabolized. In order to study the localization of sites of norepinephrine storage following its uptake in the active bat heart, tritiated norepinephrine (2.5 mCi; 0.064 mg) was given intravenously to 2 bats. Monoamine oxidase had been inhibited with pheniprazine (10 mg/kg) one hour previously to decrease metabolism of norepinephrine.

The Role of the Initiator System in the Synthesis of Acidic Multifunctional Nanoparticles Designed for Molecular Imprinting of Proteins

2020 ◽  
Vol 65 (1) ◽  
pp. 28-41
Author(s):  
Marwa Aly Ahmed ◽  
Júlia Erdőssy ◽  
Viola Horváth
Keyword(s):  
Acrylic Acid ◽  
Binding Affinity ◽  
Molecular Imprinting ◽  
Low Temperatures ◽  
Ammonium Persulfate ◽  
Sodium Bisulfite ◽  
Multifunctional Nanoparticles ◽  
High Affinity ◽  
Initiator System

Multifunctional nanoparticles have been shown earlier to bind certain proteins with high affinity and the binding affinity could be enhanced by molecular imprinting of the target protein. In this work different initiator systems were used and compared during the synthesis of poly (N-isopropylacrylamide-co-acrylic acid-co-N-tert-butylacrylamide) nanoparticles with respect to their future applicability in molecular imprinting of lysozyme. The decomposition of ammonium persulfate initiator was initiated either thermally at 60 °C or by using redox activators, namely tetramethylethylenediamine or sodium bisulfite at low temperatures. Morphology differences in the resulting nanoparticles have been revealed using scanning electron microscopy and dynamic light scattering. During polymerization the conversion of each monomer was followed in time. Striking differences were demonstrated in the incorporation rate of acrylic acid between the tetramethylethylenediamine catalyzed initiation and the other systems. This led to a completely different nanoparticle microstructure the consequence of which was the distinctly lower lysozyme binding affinity. On the contrary, the use of sodium bisulfite activation resulted in similar nanoparticle structural homogeneity and protein binding affinity as the thermal initiation.

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

scholarly journals Histone acetyltransferase TaHAG1 acts as a crucial regulator to strengthen salt tolerance of hexaploid wheat

2021 ◽  
Author(s):  
Mei Zheng ◽  
Jingchen Lin ◽  
Xingbei Liu ◽  
Wei Chu ◽  
Jinpeng Li ◽  
...  
Keyword(s):  
Salt Tolerance ◽  
Bread Wheat ◽  
Hexaploid Wheat ◽  
Histone Acetyltransferase ◽  
Tetraploid Wheat ◽  
Triticum Aestivum L ◽  
Ros Production ◽  
Signal Specificity ◽  
H3 Acetylation

Abstract Polyploidy occurs prevalently and plays an important role during plant speciation and evolution. This phenomenon suggests polyploidy could develop novel features that enable them to adapt wider range of environmental conditions compared with diploid progenitors. Bread wheat (Triticum aestivum L., BBAADD) is a typical allohexaploid species and generally exhibits greater salt tolerance than its tetraploid wheat progenitor (BBAA). However, little is known about the underlying molecular basis and the regulatory pathway of this trait. Here, we show that the histone acetyltransferase TaHAG1 acts as a crucial regulator to strengthen salt tolerance of hexaploid wheat. Salinity-induced TaHAG1 expression was associated with tolerance variation in polyploidy wheat. Overexpression, silencing and CRISPR-mediated knockout of TaHAG1 validated the role of TaHAG1 in salinity tolerance of wheat. TaHAG1 contributed to salt tolerance by modulating ROS production and signal specificity. Moreover, TaHAG1 directly targeted a subset of genes that are responsible for hydrogen peroxide production, and enrichment of TaHAG1 triggered increased H3 acetylation and transcriptional upregulation of these loci under salt stress. In addition, we found the salinity-induced TaHAG1-mediated ROS production pathway is involved in salt tolerance difference of wheat accessions with varying ploidy. Our findings provide insight into the molecular mechanism of how an epigenetic regulatory factor facilitates adaptability of polyploidy wheat and highlights this epigenetic modulator as a strategy for salt tolerance breeding in bread wheat.

scholarly journals Impact of Environmental Factors on Stilbene Biosynthesis

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 90
Author(s):  
Alessio Valletta ◽  
Lorenzo Maria Iozia ◽  
Francesca Leonelli
Keyword(s):  
Environmental Factors ◽  
Biosynthetic Pathway ◽  
In Planta ◽  
Organ Cultures ◽  
Related Plant ◽  
Valuable Compounds ◽  
Stilbene Compounds ◽  
Stilbene Biosynthesis ◽  
Abiotic Environmental Factors

Stilbenes are a small family of polyphenolic secondary metabolites that can be found in several distantly related plant species. These compounds act as phytoalexins, playing a crucial role in plant defense against phytopathogens, as well as being involved in the adaptation of plants to abiotic environmental factors. Among stilbenes, trans-resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds were subjected to investigations concerning their bioactivity. This review presents the most updated knowledge of the stilbene biosynthetic pathway, also focusing on the role of several environmental factors in eliciting stilbenes biosynthesis. The effects of ultraviolet radiation, visible light, ultrasonication, mechanical stress, salt stress, drought, temperature, ozone, and biotic stress are reviewed in the context of enhancing stilbene biosynthesis, both in planta and in plant cell and organ cultures. This knowledge may shed some light on stilbene biological roles and represents a useful tool to increase the accumulation of these valuable compounds.

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