新疆盐生植物车前PmNHX1基因的克隆及生物信息学分析

盐分对植物的伤害主要是Na+引起的,而Na+/H+逆向运输蛋白催化Na+/H+逆向跨膜运输,从而使质膜上Na+运出细胞和液泡膜中的Na+区隔化。这是植物尤其是盐生植物抵御盐胁迫的主要方式之一。根据不同植物编码液泡膜逆向运输蛋白基因的保守序列,设计简并引物,采用RT-PCR和RACE技术,首次从新疆盐生植物车前（Plantago maritima）中克隆到Na+/H+逆向运输蛋白基因的cDNA全长2464 bp,命名为PmNHX1(GenBank登录号：EU233808),该基因编码区长为1 662bp,编码553个氨基酸,理论分子量为61.16kDa,等电点为7.22。数据分析结果显示,该蛋白质主要定位于液泡膜上,由12个序列保守的跨膜结构域组成,其中TM3跨膜结构域上存在“LFFIYLLPPI”-氨氯吡嗪咪结合域,并且该位点与Na+有竞争作用。PmNHX1逆向运输蛋白与其他植物逆向运输蛋白的氨基酸同源性为64％~80％。通过生物信息学方法对其理化性质和功能分析进行预测,这为进一步研究转耐盐基因PmNHX1及其功能鉴定奠定了基础。     

Introduction of a Na+/H+ antiporter gene from Atriplex gmelini confers salt tolerance to rice

We engineered a salt-sensitive rice cultivar (Oryza sativa cv. Kinuhikari) to express a vacuolar-type Na+/H+ antiporter gene from a halophytic plant, Atriplex gmelini (AgNHX1). The activity of the vacuolar-type Na+/H+ antiporter in the transgenic rice plants was eight-fold higher than that in wild-type rice plants. Salt tolerance assays followed by non-stress treatments showed that the transgenic plants overexpressing AgNHX1 could survive under conditions of 300 mM NaCl for 3 days while the wild-type rice plants could not. These results indicate that overexpression of the Na+/H+ antiporter gene in rice plants significantly improves their salt tolerance.     

Na+/H+ 逆向转运蛋白与植物耐盐性关系

Na+/H+ 逆向转运蛋白与植物的耐盐性有密切的关系。在高等植物体内,主要存在两种Na+/H+ 逆向转运蛋白,分别为位于细胞质膜上的逆向转运蛋白SOS1,以及存在于液泡膜上的AtNHX1。质膜Na+/H+ 逆向转运蛋白主要负责Na+ 的外排,液泡膜Na+/H+ 逆向转运蛋白主要负责把Na+ 区隔化入液泡。过量表达质膜Na+/H+ 逆向转运蛋白SOS1或液泡膜Na+/H+ 逆向转运蛋白AtNHX1能够明显提高植物的耐盐性。本文对植物中Na+/H+ 逆向转运蛋白及其与植物耐盐性之间的关系研究最新进展作一概述。     

植物Na+/H+逆向转运蛋白研究进展

盐胁迫主要由Na 引起,过高的Na 浓度引起的离子毒害,渗透胁迫和K ／Na 比率的不平衡使植物新陈代谢异常,这是对大多数器官造成伤害的原因。植物抵御盐胁迫的主要方式是将细胞内过多的Na 从质膜向细胞外排放和将Na 在液泡中区隔化,这一过程是由Na ／H 逆向转运蛋白完成的。本文概述了植物中Na ／H 逆向转运蛋白的发现、特征、分子生物学方面的研究,以及Na ／H 逆向转运蛋白在植物耐盐性中的重要作用。     

植物Na+/H+逆向转运蛋白研究进展

盐胁迫主要由Na+引起,过高的Na+浓度引起的离子毒害,渗透胁迫和K+/Na+比率的不平衡使植物新陈代谢异常,这是对大多数器官造成伤害的原因。植物抵御盐胁迫的主要方式是将细胞内过多的Na+从质膜向细胞外排放和将Na+在液泡中区隔化,这一过程是由Na+/H+ 逆向转运蛋白完成的。本文概述了植物中Na+/H+ 逆向转运蛋白的发现、特征、分子生物学方面的研究,以及Na+/H+ 逆向转运蛋白在植物耐盐性中的重要作用。     

The Na+,K+/H+ -antiporter Nha1 influences the plasma membrane potential of Saccharomyces cerevisiae

There are three different sodium transport systems (Ena1-4p, Nha1p, Nhx1p) in Saccharomyces cerevisiae. The effect of their absence on the tolerance to alkali-metal cations and on the membrane potential was studied. All three sodium transporters were found to participate in the maintenance of Na+, Li+, K+ and Cs+ homeostasis. Measurements of the distribution of a fluorescent potentiometric probe (diS-C3(3) assay) in cell suspensions showed that the lack of all three transporters depolarizes the plasma membrane. The overexpression of the Na+,K+/H+ antiporter Nha1 resulted in the hyperpolarization of the plasma membrane and consequently increased the sensitivity to Cs+, Tl+ and hygromycin B. This is the first evidence that the activity of a Na+,K+/H+ antiporter could play a role in the homeostatic regulation of the plasma membrane potential in yeast cells.     

Characterization of the ion transport activity of the budding yeast Na+/H+ antiporter, Nha1p, using isolated secretory vesicles

The Saccharomyces cerevisiae Nha1p, a plasma membrane protein belonging to the monovalent cation/proton antiporter family, plays a key role in the salt tolerance and pH regulation of cells. We examined the molecular function of Nha1p by using secretory vesicles isolated from a temperature sensitive secretory mutant, sec4-2, in vitro. The isolated secretory vesicles contained newly synthesized Nha1p en route to the plasma membrane and showed antiporter activity exchanging H+ for monovalent alkali metal cations. An amino acid substitution in Nha1p (D266N, Asp-266 to Asn) almost completely abolished the Na+/H+ but not K+/H+ antiport activity, confirming the validity of this assay system as well as the functional importance of Asp-266, especially for selectivity of substrate cations. Nha1p catalyzes transport of Na+ and K+ with similar affinity (12.7 mM and 12.4 mM), and with lower affinity for Rb+ and Li+. Nha1p activity is associated with a net charge movement across the membrane, transporting more protons per single sodium ion (i.e., electrogenic). This feature is similar to the bacterial Na+/H+ antiporters, whereas other known eukaryotic Na+/H+ antiporters are electroneutral. The ion selectivity and the stoichiometry suggest a unique physiological role of Nha1p which is distinct from that of other known Na+/H+ antiporters.     

AtNHX8, a member of the monovalent cation: proton antiporter-1 family in Arabidopsis thaliana, encodes a putative Li/H antiporter

The Arabidopsis monovalent cation:proton antiporter-1 (CPA1) family includes eight members, AtNHX1-8. AtNHX1 and AtNHX7/SOS1 have been well characterized as tonoplast and plasma membrane Na+/H+ antiporters, respectively. The proteins AtNHX2-6 have been phylogenetically linked to AtNHX1, while AtNHX8 appears to be related to AtNHX7/SOS1. Here we report functional characterization of AtNHX8. AtNHX8 T-DNA insertion mutants are hypersensitive to lithium ions (Li+) relative to wild-type plants, but not to the other metal ions such as sodium (Na+), potassium (K+) and caesium (Cs+). AtNHX8 overexpression in a triple-deletion yeast mutant AXT3 that exhibits defective Na+/Li+ transport specifically suppresses sensitivity to Li+, but does not affect Na+ sensitivity. Likewise, AtNHX8 overexpression complemented sensitivity to Li+, but not Na+, in sos1-1 mutant seedlings, and increased Li+ tolerance of both the sos1-1 mutant and wild-type seedlings. Results of Li+ and K+ measurement of loss-of-function and gain-of-function mutants indicate that AtNHX8 may be responsible for Li+ extrusion, and may be able to maintain K+ acquisition and intracellular ion homeostasis. Subcellular localization of the AtNHX8-enhanced green fluorescent protein (EGFP) fusion protein suggested that AtNHX8 protein is targeted to the plasma membrane. Taken together, our findings suggest that AtNHX8 encodes a putative plasma membrane Li+/H+ antiporter that functions in Li detoxification and ion homeostasis in Arabidopsis.     

Biochemical characterization of the amiloride-sensitive Na+/H+ antiport in Chinese hamster lung fibroblasts

Net H+ fluxes across the plasma membrane of Chinese hamster lung fibroblasts (CC139) were monitored by pH-stat titration. Na+-depleted cells release H+ upon addition of Na+. Conversely Na+- or Li+-loaded cells take up H+ from the medium when shifted to a Na+,Li+-free medium. This reversible Na+ (or Li+)-dependent H+ flux is inhibited by amiloride and does not occur in digitonin-permeabilized cells. A similar Na+/H+ exchanger was identified in vascular smooth muscle cells, corneal and aortic endothelial cells, lens epithelial cells of bovine origin, and human platelets. Kinetic studies carried out with CC139 cells indicate the following properties: 1) half-saturation of the system is observed at pH = 7.8, in the absence of Na+; 2) external Na+ stimulates H+ release and inhibits H+ uptake in a competitive manner (Ki = 2-3 mM); 3) amiloride is a competitive inhibitor for Na+ (Ki congruent to 1 microM) and a noncompetitive inhibitor for H+; 4) a coupling ratio of 1.3 +/- 0.3 for the H+/Li+ exchange suggests a stoichiometry of 1:1. We conclude that CC139 cells possess in their plasma membrane a reversible, electroneutral, and amiloride-sensitive Na+/H+ antiporter, with two distinct and mutually exclusive binding sites for Na+ and H+. The rapid stimulation of the Na+/H+ antiporter in G0/G1-arrested CC139 cells upon addition of growth factors, together with the fact that intracellular H+ concentration is, under physiological conditions, around the apparent K0.5 of the system, strongly suggests a key role of this antiport in pHi regulation and mitogen action.     

Proton permeability of the plasma membrane of rat cortical synaptosomes

1. Transmembrane pH gradients (acidic inside) and electrical gradients (negative inside) were estimated in cortical synaptosomes from the distribution of the weak base methylamine and the lipophilic cation tetraphenylphosphonium, respectively. 2. Acidic interior pH gradients were produced by outwardly directed K+ gradients in Na+-free media. External K+ accelerated the dissipation of preformed H+ gradients. The appearance of H+ in the medium was directly demonstrated by pH-stat titration of a weakly buffered medium. Amiloride failed to inhibit K+-induced H+ release. 3. Elevating K+ in the absence of Na+ did not affect the endogenous contents of noradrenaline, dopamine, and serotonin, as determined by high-performance liquid chromatography with electrochemical detection. 4. H+ diffusion potentials were generated when outwardly directed H+ gradients were imposed onto the plasma membrane indicating an electrogenic H+ efflux which is not coupled to other ions. 5. At low K+ in the Na+-free sucrose medium, the plasma membrane potential Em (derived from distribution of tetraphenylphosphorium cation) did not approach a value for EK, the K+ equilibrium potential (calculated from K+ gradients). The deviation of Em from EK could be quantitatively described by a modified constant-field equation, taking a relative H+/K+ permeability coefficient of 12,400 into consideration. 6. It is concluded that synaptosomes have a H+ conductance pathway in their plasma membrane in addition to the Na+/H+ antiporter. H+ influx is driven by and leads to a reduction of Em. K+/H+ exchange resulted from the electrical coupling of K+ and H+ fluxes via parallel K+ and H+ channels. Since the Na+/H+ antiporter counteracts passive equilibration of H+ under physiological conditions, a continuous cycling of H+ across the plasma membrane will take place. A possible physiological role of the H+ leak in pHi regulation is discussed.     

Na+/H+ antiporter activity in hamster embryos is activated during fertilization

This study characterized the activation of the regulatory activity of the Na+/H+ antiporter during fertilization of hamster embryos. Hamster oocytes appeared to lack any mechanism for the regulation of intracellular pH in the acid range. Similarly, no Na+/H+ antiporter activity could be detected in embryos that were collected from the reproductive tract between 1 and 5 h post-egg activation (PEA). Activity of the Na+/H+ antiporter was first detected in embryos collected at 5.5 h PEA and gradually increased to reach maximal activity in embryos collected at 7 h PEA. Parthenogenetically activated one-cell and two-cell embryos demonstrate Na+/H+ antiporter activity, indicating that antiporter activity is maternally derived and initiated by activation of the egg. The inability of cycloheximide, colchicine, or cytochalasin D to affect initiation of antiporter activity indicates that antiporter appearance is not dependent on the synthesis of new protein or recruitment of existing protein to the cell membrane. In contrast, incubation of one-cell embryos with sphingosine did inhibit the appearance of Na+/H+ antiporter activity, showing that inhibition of normal protein kinase C activity is detrimental to antiporter function. Furthermore, incubation of oocytes with a phorbol ester which stimulates protein kinase C activity induced Na+/H+ antiporter activity in oocytes in which the activity was previously absent. Incubation with an intracellular calcium chelator also reduced the appearance of antiporter activity. Taken together, these data indicate that the appearance of Na+/H+ antiporter activity following egg activation may be due, at least in part, to regulation by protein kinase C and intracellular calcium levels.     

花烟草NaNHX1基因的克隆及其在非生物胁迫下的表达模式

植物NHX家族基因,在植物的生长发育以及生物与非生物胁迫的应答反应中发挥着十分重要的作用。为了探究花烟草Na+/H+逆向转运蛋白的生理功能,为花烟草耐盐分子机制的研究提供参考。采用同源克隆的方法进行基因克隆,对花烟草进行非生物胁迫,并运用qPCR的方法进行基因表达模式分析。结果表明,从花烟草(Nicotiana alata)中克隆了一个属于Na+/H+逆向转运蛋白家族的基因NaNHX1。该基因的开放阅读框全长为1 599 bp,编码了532个氨基酸残基。生物信息学分析结果表明,该基因编码的蛋白分子量为58.4 kD,等电点为5.66;具有Na+/H+逆向转运蛋白家族典型的保守结构域NhaP2;该蛋白属于疏水性蛋白,包含10个跨膜区。NaNHX1基因主要定位于细胞质膜,并含有多个磷酸化位点。同源性分析的结果显示,NaNHX1基因与美花烟草(Nicotiana sylvestris)、茸毛烟草(Nicotiana tomentosiformis)以及番茄(Solanum lycoperisicum)NHX基因的亲缘关系最近,而与拟南芥的NHX基因同源性最低。NaNHX1基因的表达具有组织表达特异性,花中表达量最高,茎中次之,根和叶中表达量较低。在高盐、干旱、低温、ABA、低钾及H2O2等非生物胁迫下,NaNHX1的表达呈现3种不同的表达模式。其中,对高盐及低钾胁迫的响应强烈。本研究的结果表明,NaNHX1基因属于Na+/H+逆向转运蛋白家族,可能参与了花烟草高盐和低钾胁迫,以及其它非生物胁迫响应在内的众多生理过程。     

Lobster hepatopancreatic epithelial single cell suspensions as models for electrogenic sodium-proton exchange

Sodium-proton antiporters, also called Na+/H+ exchangers (NHE), are vital transmembrane proteins involved in multiple cellular functions including transepithelial ion transport and Na+ homeostasis of cells throughout the biological kingdom. Na+/H+ exchange is accelerated by cytosolic acidification and also by osmotically induced cell shrinking, thereby promoting recovery of the physiological pHi and volume. Eight isoforms of Na+/H+ exchangers have been cloned and characterized to date and share the same overall structure, but exhibit differences with respect to cellular localization, kinetic variables and plasma membrane targeting, in polarized epithelial cells. The electrogenic Na+ absorption across tight epithelia from invertebrates follow significantly different principles from the electroneutral Na+/H+ antiporter found in vertebrates. In all invertebrate cells examined, the antiporter displayed a 2Na+/1H+ transport stoichiometry and this transport was markedly inhibited by exogenous calcium and zinc. Na+/H+ exchangers (NHE) are present in crustacean hepatopancreatic cell type suspensions and are believed to function in acid-base regulation by driving the extrusion of protons across the hepatopancreatic epithelium in exchange for Na+ in the sea water. A brief review of current knowledge about Na+/H+ exchangers has been presented. In addition, understanding of hepatopancreatic Na+/H+ exchange is described as obtained after isolation of purified E-, R-, F- and B-cell suspensions from the whole organ by centrifugal elutriation.     

Endogenous energy supply to the plasma membrane of dark aerobic cyanobacterium Anacystis nidulans: ATPase-independent efflux of H+ and Na+ from respiring cells

The ejection of protons from oxygen-pulsed cells and the gradients of Na+ concentration (Na+o/Na+i at 150 mM external NaCl) and proton electrochemical potential (delta mu H+) across the plasma membrane of Anacystis nidulans were studied in response to dark endogenous energy supply. Saturating concentrations of the F0F1-ATPase inhibitors dicyclohexylcarbodiimide (F0) and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (F1) eliminated oxidative phosphorylation and lowered the ATP level from 2.6 +/- 0.15 to 0.7 +/- 0.1 nmol/mg dry wt while overall O2 uptake and delta mu H+ were much less affected. H+ efflux was inhibited only 60 to 75%. Aerobic Na+o/Na+i ratios (5.9 +/- 0.6) under these conditions remained 50% above the anaerobic level (2.1 +/- 0.2). Increasing concentrations of the electron transport inhibitors CO and KCN depressed H+ efflux and O2 uptake in parallel, with a pronounced discontinuity of the former at inhibitor concentrations, which reduced ATP levels from 2.6 to 0.8 nmol/mg dry wt, resulting in an abrupt shift of the apparent H+/O ratios from 4.0 +/- 0.3 to 1.9 +/- 0.2. Similarly, with KCN and CO the Na+o/Na+i ratios paralleled decreasing respiration rates more closely than decreasing ATP pool sizes. Ejection of protons also was observed when intact spheroplasts were pulsed with horse heart ferrocytochrome c or ferricyanide; the former reaction was inhibited, the latter was increased, by 1 mM KCN. Measurements of the proton motive force (delta mu H+) across the plasma membrane showed a strong correlation with respiration rates rather than ATP levels. It is concluded that the plasma membrane of intact A. nidulans can be directly energized by proton-translocating respiratory electron transport in the membrane and that part of this energy may be used by a Na+/H+ antiporter for the active exclusion of Na+ from the cell interior.     

Control of the sodium-proton antiporter in human placental microvillous membranes by transport substrates

The microvillous membrane of the human placental syncytiotrophoblast contains an amiloride-inhibitable, electroneutral, Na+/H+ antiporter. The kinetic characteristics of this antiporter have been investigated to determine its response to alterations in intracellular and extracellular H+ and Na+ concentrations. Antiporter activity was measured using a pH-sensitive fluorescent probe entrapped in placental microvillous vesicles. We report here on the kinetic characterization of the antiporter, a transporter which displays simple, saturable kinetics for the external site but complex kinetics at the internal site. Measurement of the external Na+ and H+ dependences demonstrated that Na+ and H+ compete for binding to a single external binding site which displays saturation kinetics. The external Km determined for Na+ was 8.2 +/- 4.0 mM, while the external pK was 7.29 +/- 0.02. The Vmax calculated from these experiments was 0.57 +/- 0.10 nequiv./s per mg membrane protein. By contrast, the internal dependences for both Na+ and H+ showed significant deviations from simple linear kinetics. Decreasing internal pH to 6.0 stimulated Na+/H+ exchange to a greater degree than predicted for a single-site saturable binding model, in a manner which suggested allosteric activation. At the other extreme, Na+/H+ exchange ceased above an internal pH of 7.1, despite the existence of an inwardly-directed Na+ gradient. Increasing intracellular Na+ caused inhibition of Na+/H+ exchange but the intracellular Na+ dependence showed that the effect is due to a mechanism more complex than simple, competitive inhibition between Na+ and H+. These results show that the microvillous Na+/H+ antiporter is insensitive to changes in extracellular Na+ and H+ concentrations in the physiological range. Changes in intracellular Na+ and H+ however are likely to cause marked changes in antiporter activity. These characteristics suggest that cellular Na+ and H+ concentrations are tightly controlled in the placental syncytiotrophoblast and that the Na+/H+ antiporter may play a significant role in their regulation.     

Inhibition of cardiac sarcolemmal Na+/H+ antiporter by opioids.

In our routine screening of chemicals that would inhibit cardiac sarcolemmal Na+/H+ antiporter, we discovered that some of the opioids produced inhibition of cardiac sarcolemmal Na+/H+ antiporter in micromolar concentrations. Using U-50,488H, a selective kappa-opioid agonist, we characterized the nature of interaction between opioids and the Na+/H+ antiporter. The inhibitory effect of U-50,488H on Na+/H+ antiporter was immediate and reversible, and was not mediated through the interaction with the opioid receptors but due to the direct interaction of U-50,488H with the Na+/H+ antiporter. The kinetic data show that in the presence of U-50,488H the Km for Na+ was increased from 2.5 +/- 0.2 to 5.0 +/- 0.3 mM, while the Vmax (52.0 +/- 5.0 nmol.mg-1.min-1) remained the same. These results suggest that U-50,488H and Na+ compete for the same site on the antiporter. When testing the effect of U-50,488H on other transport systems of cardiac sarcolemma, we found that U-50,488H also inhibited Na+/Ca2+ antiporter and Na+/K+ pump but at much higher concentrations suggesting that U-50,488H shows some degree of selectivity for cardiac sarcolemmal Na+/H+ antiporter. When we compared the inhibitory potency of U-50,488H with amiloride and its analog, namely 5-(N,N-hexamethylene)amiloride, we found that U-50,488H (IC50 = 100 +/- 15 microM) was threefold more potent than amiloride (IC50 = 300 +/- 20 microM) but it was three-fold less potent than the amiloride analog (IC50 = 30 +/- 10 microM) in inhibiting cardiac sarcolemmal Na+/H+ antiporter. These results show that although U-50,488H is more potent than amiloride, the inhibitory characteristics of U-50,488H on cardiac sarcolemmal Na+/H+ antiporter are similar to amiloride.     

Export of Na+ from cells of the halotolerant microalga Dunaliella maritima: Na+/H+ antiporter or primary Na+-pump?

Transport of Na+ and K+ ions through the plasma membrane of intact cells of the halotolerant microalga Dunaliella maritima Massjuk was studied. Ion fluxes through the plasma membrane were induced by hyperosmotic shock (uptake of Na+ by the cells is transformed into extrusion of Na+) or by addition of K+ to a suspension of K+-deficient cells (uptake of K+ by the cells is associated with extrusion of Na+). The pathway of Na+ extrusion from the D. maritima cells does not depend on the direction or value of the proton gradient on the plasma membrane. In particular, the efficiency of Na+ extrusion was not changed at extracellular pH values varying from 6.0 to 8.0. The protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) (20 microM) and the H+-ATPase inhibitor N,N-dicyclohexyl carbodiimide (DCCD) (25 and 100 microM) inhibited accumulation of K+ by the cells but did not influence Na+ extrusion. Significant acidification of the medium did not induce a net current of Na+ from the cells through a Na+/H+ antiporter. The data indicate that the Na+/H+ antiporter of the plasma membrane of D. maritima is not responsible for Na+ extrusion from the cells. These results can be explained by the involvement of a primary electrogenic Na+ pump (a Na+-transporting ATPase) in Na+ transfer through the plasma membrane of this alga.     

Properties of two different Na+/H+ antiport systems in alkaliphilic Bacillus sp. strain C-125.

Na+/H+ antiport was studied in alkaliphilic Bacillus sp. strain C-125, its alkali-sensitive mutant 38154, and a transformant (pALK2) with recovered alkaliphily. The transformed was able to maintain an intracellular pH (pHin) that was lower than that of external milieu and contained an electrogenic Na+/H+ antiporter driven only by delta psi (membrane potential, interior negative). The activity of this delta psi-dependent Na+/H+ antiporter was highly dependent on pHin, increasing with increasing pHin, and was found only in cells grown at alkaline pH. On the other hand, the alkali-sensitive mutant, which had lost the ability to grow above pH 9.5, lacked the delta psi-dependent Na+/H+ antiporter and showed defective regulation of pHin at the alkaline pH range. However, this mutant, like the parent strain, still required sodium ions for growth and for an amino acid transport system. Moreover, another Na+/H+ antiporter, driven by the imposed delta pH (pHin > extracellular pHout), was active in this mutant strain, showing that the previously reported delta pH-dependent antiport activity is probably separate from delta psi-dependent antiporter activity. The delta pH-dependent Na+/H+ antiporter was found in cells grown at either pH 7 or pH 9. This latter antiporter was reconstituted into liposomes by using a dilution method. When a transmembrane pH gradient was applied, downhill sodium efflux was accelerated, showing that the antiporter can be reconstituted into liposomes and still retain its activity.     

质膜Na^＋／H^＋逆向转运蛋白与植物耐盐性

土壤盐碱化是造成农作物减产的主要原因之一。质膜Na^＋／H^＋逆向转运蛋白能够介导植物根部Na^＋的外排和体内Na^＋的长距离运输, 并能够调控细胞K＋的稳态平衡及细胞内pH值和Ca^2＋的转运, 因此其在植物耐盐性方面具有重要作用。该文概述了植物质膜Na^＋／H^＋逆向转运蛋白的分子结构、功能、表达调控及其与植物耐盐性关系等方面的研究进展, 并对今后有关该蛋白的主要研究方向作了分析和展望。