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A controversy of long standing in membrane electrophysio-logy is whether the sodium ion current (INa) and potassium ion current (IK) pass through the membrane in separate channels, or through a single set of channels which conduct first INa and then IK. In support of the latter hypothesis it has been noted that the sodium conductance (gNa) decline, called inactivation, proceeds with about the same time course as the potassium conductance (gK) increase. This could mean that Na+ selective channels are being converted into K+ selective channels. The hypothesis is especially interesting because of the possibility that the carrier postulated in active transport is convertible from Na+ to K+ selectivity1. An explicit statement of the single channel hypothesis and the means for disproving it were given by Mullins2. Because a single channel could not simultaneously conduct INa and IK, disproof requires that membrane conductance (gm) be made somehow to exceed the maximum value of gNa or gK. We report here that inactivation of gNa can be destroyed fairly selectively by the action from inside the axon of the unspecific proteolytic enzymes of pronase. In many cases gm after pronase treatment is greater than maximum gK before treatment, making untenable the single channel hypothesis. 相似文献
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Xiaohui Liu Shenguan Cai Gang Wang Feifei Wang Fabao Dong Michelle Mak Paul Holford Jing Ji Anya Salih Meixue Zhou Sergey Shabala Zhong-Hua Chen 《Plant Growth Regulation》2017,82(2):333-351
While the role of the vacuolar NHX Na+/H+ exchangers in plant salt tolerance has been demonstrated on numerous occasions, their control over cytosolic ionic relations has never been functionally analysed in the context of subcellular Na+ and K+ homeostasis. In this work, PutNHX1 and SeNHX1 were cloned from halophytes Puccinellia tenuiflora and Salicornia europaea and transiently expressed in Arabidopsis wild type Col-0 and the nhx1 mutant. Phylogentic analysis, topological prediction, analysis of evolutionary conservation, the topology structure and analysis of hydrophobic or polar regions of PutNHX1 and SeNHX1 indicated that they are unique tonoplast Na+/H+ antiporters with characteristics for salt tolerance. As a part of the functional assessment, cytosolic and vacuolar Na+ and K+ in different root tissues and ion fluxes from root mature zone of Col-0, nhx1 and their transgenic lines were measured. Transgenic lines sequestered large quantity of Na+ into root cell vacuoles and also promoted high cytosolic and vacuolar K+ accumulation. Expression of PutNHX1 and SeNHX1 led to significant transient root Na+ uptake in the four transgenic lines upon recovery from salt treatment. In contrast, the nhx1 mutant maintained a prolonged Na+ efflux and the nhx1:PutNHX1 and nhx1:SeNHX1 lines started to actively pump Na+ out of the cell. Overall, our findings suggest that PutNHX1 and SeNHX1 improve Na+ sequestration in the vacuole and K+ retention in the cytosol and vacuole of root cells of Arabidopsis, and that they interact with other regulatory mechanisms to provide a highly orchestrated regulation of ionic relations among intracellular cell compartments. 相似文献
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Devinder Sandhu Manju V. Pudussery Rakesh Kaundal Donald L. Suarez Amita Kaundal Rajandeep S. Sekhon 《Functional & integrative genomics》2018,18(2):141-153
One important mechanism plants use to cope with salinity is keeping the cytosolic Na+ concentration low by sequestering Na+ in vacuoles, a process facilitated by Na+/H+ exchangers (NHX). There are eight NHX genes (NHX1 through NHX8) identified and characterized in Arabidopsis thaliana. Bioinformatics analyses of the known Arabidopsis genes enabled us to identify six Medicago truncatula NHX genes (MtNHX1, MtNHX2, MtNHX3, MtNHX4, MtNHX6, and MtNHX7). Twelve transmembrane domains and an amiloride binding site were conserved in five out of six MtNHX proteins. Phylogenetic analysis involving A. thaliana, Glycine max, Phaseolus vulgaris, and M. truncatula revealed that each individual MtNHX class (class I: MtNHX1 through 4; class II: MtNHX6; class III: MtNHX7) falls under a separate clade. In a salinity-stress experiment, M. truncatula exhibited ~?20% reduction in biomass. In the salinity treatment, sodium contents increased by 178 and 75% in leaves and roots, respectively, and Cl? contents increased by 152 and 162%, respectively. Na+ exclusion may be responsible for the relatively smaller increase in Na+ concentration in roots under salt stress as compared to Cl?. Decline in tissue K+ concentration under salinity was not surprising as some antiporters play an important role in transporting both Na+ and K + . MtNHX1, MtNHX6, and MtNHX7 display high expression in roots and leaves. MtNHX3, MtNHX6, and MtNHX7 were induced in roots under salinity stress. Expression analysis results indicate that sequestering Na+ into vacuoles may not be the principal component trait of the salt tolerance mechanism in M. truncatula and other component traits may be pivotal. 相似文献
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Xin-Xia Teng Wen-Lei Cao Hong-Xia Lan Hai-Juan Tang Yong-Mei Bao Hong-Sheng Zhang 《Acta Physiologiae Plantarum》2017,39(5):113
The Na+/H+ antiporters play an important role in salt tolerance in plants. However, the functions of OsNHXs in rice except OsNHX1 have not been well studied. Using the gain- and loss-of-function strategies, we studied the potential role of OsNHX2 in salt tolerance in rice. Overexpression of OsNHX2 (OsNHX2-OE) in rice showed the significant tolerance to salt stress than wild-type plants and OsNHX2 knockdown transgenic plants (OsNHX2-KD). Under salt treatments of 300-mM NaCl for 5 days, the plant fresh weights, relative water percentages, shoot heights, Na+ contents, K+ contents, and K+/Na+ ratios in leaves of OsNHX2-OE transgenic plants were higher than those in wild-type plants, while no differences were detected in roots. K+/Na+ ratios in rice leaf mesophyll cells and bundle sheath cells were higher in OsNHX2-OE transgenic plants than in wild-type plants and OsNHX2-KD transgenic plants. Our data indicate that OsNHX2 plays an important role in salt stress based on leaf mesophyll cells and bundle sheath cells and can be served in genetically engineering crop plants with enhanced salt tolerance. 相似文献
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Muhammad A. Asif Rhiannon K. Schilling Joanne Tilbrook Chris Brien Kate Dowling Huwaida Rabie Laura Short Christine Trittermann Alexandre Garcia Edward G. Barrett-Lennard Bettina Berger Diane E. Mather Matthew Gilliham Delphine Fleury Mark Tester Stuart J. Roy Allison S. Pearson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2018,131(10):2179-2196
Key message
Novel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields.Abstract
Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur?×?Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity (QG(1–5).asl-7A), one for leaf Na+ exclusion (QNa.asl-7A) and four for leaf K+ accumulation (QK.asl-2B.1, QK.asl-2B.2, QK.asl-5A and QK:Na.asl-6A). The beneficial allele for QG(1–5).asl-7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na+ exclusion and/or K+ maintenance at three QTL (QNa.asl-7A, QK.asl-2B.2 and QK:Na.asl-6A) excluded more Na+ or accumulated more K+ compared to lines without these alleles. Importantly, the QK.asl-2B.2 allele for higher K+ accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.9.
Casuarina equisetifolia is widely planted in coastal areas of tropical and subtropical regions as windbreaks or to stabilize dunes against wind erosion due to its high salt tolerance and nitrogen-fixing ability. To investigate the mechanisms responsible for its salt tolerance, we examined growth, mineral composition, expression of genes for sodium (Na+) and potassium (K+) transport proteins, and antioxidant responses under NaCl treatments. Increasing NaCl concentrations inhibited lateral root elongation and decreased plant height, length of internodes, and numbers of branches and twigs. The Na+ content significantly increased whereas the K+ content significantly decreased in both shoots and roots with increasing external NaCl concentration, resulting in a significant increase in Na+/K+ ratio. Most of the Na+/H+ antiporter genes (NHXs) were obviously upregulated in roots after 24 and 168 h of salt stress, and NHX7 was especially induced after 168 h. Almost all salt overly sensitive (SOS) genes were induced after 168-h treatment. Additionally, activities of superoxide dismutase, glutathione peroxidase, and catalase were significantly changed in shoots and roots under salt stress. Hence, we conclude that salinity tolerance of C. equisetifolia mainly relied on sequestering excess Na+ into vacuoles and on induced expression of NHX and SOS genes in roots and thus the maintenance of sufficient K+ content in shoots. 相似文献
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Wenqiang Wang Fengxia Tian Qunqun Hao Yangyang Han Qinxue Li Xin Wang Wenlong Wang Yong Wang Wei Wang 《Acta Physiologiae Plantarum》2018,40(2):39
Salt stress inhibited the growth of both tasg1 and wild-type (WT) wheat seedlings, but the inhibition in tasg1 plants was relatively weaker than that of WT. Compared to the WT, the chlorophyll content, thylakoid membrane polypeptides, Hill reaction activity, actual photochemical efficiency of PSII (ΦPSII), and Mg2+- and Ca2+-ATPase activities were higher in tasg1 under salt stress. At the same time, the photosynthetic activity of the tasg1 was significantly higher than that of WT. In addition, tasg1 plants displayed relatively less accumulation of reactive oxygen species and oxidative damage accompanied by higher activity of some antioxidant enzymes, and the up-regulation of antioxidant genes further demonstrated the improvement of antioxidant activity in tasg1 under salt stress. Furthermore, tasg1 plants also showed relatively weaker Na+ fluorescence and lower Na+ content, but relatively higher content of K+ in their roots and shoots, and then, the roots of tasg1 plants enhanced net outward Na+ flux and a correspondingly increased net inward K+ flux during salt stress. This might be associated with the relatively higher activity of H+-ATPase in tasg1 plants. These results suggest that the improved antioxidant competence and Na+/K+ ion homeostasis play an important role in the enhanced salinity tolerance of tasg1 plants. 相似文献
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K. Punyawaew D. Suriya-arunroj M. Siangliw M. Thida J. Lanceras-Siangliw S. Fukai T. Toojinda 《Molecular breeding : new strategies in plant improvement》2016,36(11):150
Saltol, the major salinity tolerance quantitative trait loci (QTL) in rice, was introgressed from IR66946-3R-230-1-1 (FL530) into Khao Dawk Mali 105 (KDMl105) by two rounds of marker-assisted backcrossing (MAB). Twenty-eight BC2F2 introgression lines (BILs) with positive Saltol allele (BIL+Saltol) and 19 BILs with negative Saltol allele (BIL?Saltol) were validated for the effect of Saltol as key salinity tolerant trait at seedling stage. A hydrophonic system with salt stress of 12 dS m?1 (130 mM Na+) was conducted, and significant differences between BILs+Saltol and BILs?Saltol were observed for the period of plant survival (PPS), total K+ (T-K+) and Na+ (T-Na+) concentration, whole plant Na+-K+ ratio (T-Na+/K+), shoot Na+ (S-Na+) and K+ (S-K+) concentration, and shoot Na+-K+ ratio (S-Na+/K+). BILs+Saltol displayed higher PPS, uptake less Na+ (T-Na+; 43.4 ppm), and more K+ (T-K+; 30.9 ppm), while the BILs?Saltol uptake more Na+ (T-Na+; 45.7 ppm) and less K+ (T-K+; 28.2 ppm). Direct effects on PPS and salt injury score (SIS) were observed, indicating Na+/K+ homeostasis mechanism by the Saltol under hydrophonic salt stress. All BILs+Saltol recovered KDML105 cooking quality profile such as low apparent amylose content (AAC), high score of alkaline spreading value (ASV), intermediate gel consistency (GC), and strong fragrance. However, variation in agronomic traits was observed. The possibility of lowering S-Na+/K+ ratio under salt stress at seedling stage in KDML105 by introgression of the Saltol was demonstrated. Currently, BC2F7 of the BIL+Saltol selected lines are being tested for salinity tolerance in the salt-affected areas in the northeast of Thailand. 相似文献
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Alicia Gutnisky María Graciela López Ordieres Georgina Rodríguez de Lores Arnaiz 《Neurochemical research》2016,41(6):1274-1280
Neurotensin behaves as a neuromodulator or as a neurotransmitter interacting with NTS1 and NTS2 receptors. Neurotensin in vitro inhibits synaptosomal membrane Na+, K+-ATPase activity. This effect is prevented by administration of SR 48692 (antagonist for NTS1 receptor). The administration of levocabastine (antagonist for NTS2 receptor) does not prevent Na+, K+-ATPase inhibition by neurotensin when the enzyme is assayed with ATP as substrate. Herein levocabastine effect on Na+, K+-ATPase K+ site was explored. For this purpose, levocabastine was administered to rats and K+-p-nitrophenylphosphatase (K+-p-NPPase) activity in synaptosomal membranes and [3H]-ouabain binding to cerebral cortex membranes were assayed in the absence (basal) and in the presence of neurotensin. Male Wistar rats were administered with levocabastine (50 μg/kg, i.p., 30 min) or the vehicle (saline solution). Synaptosomal membranes were obtained from cerebral cortex by differential and gradient centrifugation. The activity of K+-p-NPPase was determined in media laking or containing ATP plus NaCl. In such phosphorylating condition enzyme behaviour resembles that observed when ATP hydrolyses is recorded. In the absence of ATP plus NaCl, K+-p-NPPase activity was similar for levocabastine or vehicle injected (roughly 11 μmole hydrolyzed substrate per mg protein per hour). Such value remained unaltered by the presence of 3.5 × 10?6 M neurotensin. In the phosphorylating medium, neurotensin decreased (32 %) the enzyme activity in membranes obtained from rats injected with the vehicle but failed to alter those obtained from rats injected with levocabastine. Levocabastine administration enhanced (50 %) basal [3H]-ouabain binding to cerebral cortex membranes but failed to modify neurotensin inhibitory effect on this ligand binding. It is concluded that NTS2 receptor blockade modifies the properties of neuronal Na+, K+-ATPase and that neurotensin effect on Na+, K+-ATPase involves NTS1 receptor and -at least partially- NTS2 receptor. 相似文献
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Sixty seven-days-old plants of Ammi majus L. were subjected for 46 d to sand culture at varying concentrations of NaCl, i.e. 0 (control), 40, 80, 120, and 160 mM. Increasing salt concentrations caused a significant reduction in fresh and dry masses of both shoots and roots as well as seed yield. However, the adverse effect of salt was more pronounced on seed yield than biomass production at the vegetative stage. Calculated 50 % reduction in shoot dry mass occurred at 156 mM (ca.15.6 mS cm?1), whereas that in seed yield was at 104 mM (ca.10.4 mS cm?1). As in most glycophytes, Na+ and Cl? in both shoots and roots increased, whereas K+ and Ca2+ decreased consistently with the successive increase in salt level of the growth medium. Plants of A. majusmaintained markedly higher K+/Na+ ratios in the shoots than those in the roots, and the ratio remained more than 1 even at the highest external salt level (160 mM). Net photosynthetic (PN) and transpiration (E) rates remained unaffected at increasing NaCl, and thus these attributes had a negative association with salt tolerance of A. majus. Proline content in the shoots increased markedly at the higher concentrations of salt. Essential oil content in the seed decreased consistently with increase in external salt level. Overall, A. majusis a moderately salt tolerant crop whose response to salinity is associated with maintenance of high shoot K+/Na+ ratio and accumulation of proline in shoots, but PN had a negative association with the salt tolerance of this crop. 相似文献
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Yu. V. Balnokin N. A. Myasoedov Z. Sh. Shamsutdinov N. Z. Shamsutdinov 《Russian Journal of Plant Physiology》2005,52(6):779-787
The contents of Na+, K+, water, and dry matter were measured in leaves and roots of euhalophytes Salicornia europaea L. and Climacoptera lanata (Pall.) Botsch featuring succulent and xeromorphic cell structures, respectively, as well as in saltbush Atriplex micrantha C.A. Mey, a halophyte having bladder-like salt glands on their leaves. All three species were able to accumulate Na+ in their tissues. The Na+ content in organs increased with elevation of NaCl concentration in the substrate, the concentrations of Na+ being higher in leaves than in roots. When these halophytes were grown on a NaCl-free substrate, a trend toward K+ accumulation was observed and was better pronounced in leaves than in roots. Particularly high K+ concentrations were accumulated in Salicornia leaves. There were no principal differences in the partitioning of Na+ and K+ between organs of three halophyte species representing different ecological groups. At all substrate concentrations of NaCl, the total content of Na+ and K+ in leaves was higher than in roots. This distribution pattern persisted in Atriplex possessing salt glands, as well as in euhalophytes Salicornia and Climacoptera. The physiological significance of such universal pattern of ion accumulation and distribution among organs in halophytes is related to the necessity of water absorption by roots, its transport to shoots, and maintenance of sufficient cell water content in all organs under high soil salinity. 相似文献
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Wei-Wei Zhang Jing-Jing Meng Jin-Yi Xing Sha Yang Feng Guo Xin-Guo Li Shu-Bo Wan 《Journal of Plant Biology》2017,60(3):259-267
High salinity is the one of important factors limiting plant growth and crop production. Many NHX-type antiporters have been reported to catalyze K+/H+ exchange to mediate salt stress. This study shows that an NHX gene from Arachis hypogaea L. has an important role in K+ uptake and transport, which affects K+ accumulation and plant salt tolerance. When overexpressing AhNHX1, the growth of tobacco seedlings is improved with longer roots and a higher fresh weight than the wild type (WT) under NaCl treatment. Meanwhile, when exposed to NaCl stress, the transgenic seedlings had higher K+/H+ antiporter activity and their roots got more K+ uptake. NaCl stress could induce higher K+ accumulation in the roots, stems, and leaves of transgenic tobacco seedlings but not Na+ accumulation, thus, leading to a higher K+/Na+ ratio in the transgenic seedlings. Additionally, the AKT1, HAK1, SKOR, and KEA genes, which are involved in K+ uptake or transport, were induced by NaCl stress and kept higher expression levels in transgenic seedlings than in WT seedlings. The H+-ATPase and H+-PPase activities were also higher in transgenic seedlings than in the WT seedlings under NaCl stress. Simultaneously, overexpression of AhNHX1 increased the relative distribution of K+ in the aerial parts of the seedlings under NaCl stress. These results showed that AhNHX1 catalyzed the K+/H+ antiporter and enhanced tobacco tolerance to salt stress by increasing K+ uptake and transport. 相似文献
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Hui Li Wei Liu Qing-Song Yang Jing Lin You-Hong Chang 《Plant Molecular Biology Reporter》2018,36(3):439-450
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N. Naresh Babu K. K. Vinod S. L. Krishnamurthy S. Gopala Krishnan Ashutosh Yadav P. K. Bhowmick M. Nagarajan N. K. Singh K. V. Prabhu A. K. Singh 《Journal of plant biochemistry and biotechnology.》2017,26(3):310-320
A set of 84 diverse rice genotypes were assessed for seedling stage salt tolerance and their genetic diversity using 41 polymorphic SSR markers comprising of 19 Saltol QTL linked and 22 random markers. Phenotypic screening under hydroponics identified three indica landraces (Badami, Shah Pasand and Pechi Badam), two Oryza rufipogon accessions (NKSWR2 and NKSWR17) and one each of Basmati rice (Seond Basmati) and japonica cultivars (Tompha Khau) as salt tolerant, having similar tolerance as of Pokkali and FL478. Among the salt tolerant genotypes, biomass showed positive correlation with shoot fresh weight and negative association with root and shoot Na+ content. The results indicated repression of Na+ loading within the tolerant plants. Linkage disequilibrium (LD) of the Saltol linked markers was weak, suggestive of high fragmentation of Pokkali haplotype, a result of evolutionary active recombination events. Poor haplotype structure of the Saltol region, may reduce its usefulness in marker assisted breeding programmes, if the target foreground markers chosen are wide apart. LD mapping identified eight robust marker-trait associations (QTLs), of which RM10927 was found linked to root and shoot Na+ content and RM10871 with shoot Na+/K+ ratio. RM271 on chromosome 10, an extra Saltol marker, was found associated to root Na+/K+ ratio. This marker showed a distinct allele among O. rufipogon accessions. There were also other novel loci detected on chromosomes 2, 5 and 10 influencing salt tolerance in the tested germplasm. Although Saltol remained as the key locus, the role of other genomic regions cannot be neglected in tailoring seedling stage salt tolerance in rice. 相似文献