Overexpression of Arabidopsis thaliana Na+/H+ antiporter gene enhanced salt resistance in transgenic poplar (Populus?×?euramericana ‘Neva’)

Salinity is a major abiotic stress factor limiting plant growth and productivity. One possible method to enhance plant salt-resistance is to compartmentalize sodium ions away from the cytosol. In the present work, a vacuolar Na⁺/H⁺ antiporter gene AtNHX1 from Arabidopsis thaliana, was transferred into Populus × euramericana ‘Neva’ by Agrobacterium tumefaciens in order to enhance poplar salt-resistance. The results showed that the transgenic poplar were more resistant to NaCl than the wild-type (WT) in greenhouse condition. Compared with the WT, plant growth and photosynthetic capacity of the transgenic plants were enhanced, and the transgenic plants accumulated more Na⁺ and K⁺ in roots and leaves under the same NaCl condition, whereas malondialdehyde and relative electrical conductivity were lower. All of these properties of the transgenic poplar were likely to be a consequence of the overexpression of AtNHX1 caused Na⁺ sequestration in the vacuoles and improved K⁺ absorption, thus reducing their toxic effects. These results indicated overexpression of the AtNHX1 enhanced salt-resistance of poplar, and AtNHX1 played an important role in the compartmentation of Na⁺ into the vacuoles. Therefore, this study provides an effective way for improving salt resistance in trees.     

(Na+/K+)-ATPase研究概况

本文概述(Na⁺/K⁺)-ATPase的一般分子性质。介绍神经元和脂肪细胞中两种不同分子形式(Na⁺/K⁺)-ATPase的分离鉴定和功能性质,以及(Na⁺/K⁺)-ATPase主要功能亚基一级序列和高级结构研究所取得的一些进展。     

西伯利亚白刺质膜Na+/H+逆向转运蛋白基因NsSOS1的分离及表达分析

采用同源克隆技术分离了西伯利亚白刺(Nitraria sibirica)质膜Na~+/H~+逆向转运蛋白基因NsSOS1,并对其在不同胁迫条件下的表达特性进行了分析。NsSOS1包含3 516bp开放阅读框(ORF),编码1 171个氨基酸,蛋白分子量为128.34kD。生物信息学分析显示,NsSOS1包含12个跨膜结构域,具有植物SOS1蛋白的保守结构域。系统发育分析表明,NsSOS1与其他植物质膜Na~+/H~+逆向转运蛋白处于同一个次级分化群,与锦葵科海滨锦葵KvSOS1亲缘关系较近。实时荧光定量RT-PCR分析显示,NsSOS1基因在西伯利亚白刺的根和叶中表达量较高;其表达受到非生物胁迫(NaCl、低温、干旱)和外源激素(MeJA和GA)的诱导,表明NsSOS1基因在西伯利亚白刺抵御逆境胁迫过程中发挥重要作用。     

Na+/H+逆向转运蛋白和植物耐盐性

Na⁺H⁺逆向转运蛋白对植物耐盐起着重要作用 ,它利用质膜H⁺ATPase或液泡膜H⁺ATPase及Ppiase泵H+产生的驱动力把Na⁺排出细胞或在液泡中区隔化以消除Na⁺的毒害。主要讨论植物中Na⁺H⁺逆向转运蛋白研究在分子水平的最新进展.     

Calculations of K+, Na+, and Cl? fluxes across cell membrane with Na+/K+ pump, NKCC, NC cotransport and ionic channels with non-Goldman rectification in K+-channels: Normal and apoptotic cells

The balance of K⁺, Na⁺, and Cl⁻ fluxes across the cell membrane with the Na⁺/K⁺ pump, ion channels, and Na⁺K⁺2Cl⁻ (NKCC) and Na⁺-Cl⁻ (NC) cotransport was calculated to determine the mechanism of cell shrinkage in apoptosis. It is shown that all unidirectional K⁺, Na⁺, and Cl⁻ fluxes; the ion channel permeability; and the membrane potential can be found using the principle of the flux balance if the following experimental data are known: K⁺, Na⁺, and Cl⁻ concentrations in cell water; total Cl⁻ flux; total K⁺ influx; and the ouabain-inhibited pump component of the Rb⁺(K⁺) influx. The change in different ionic pathways during apoptosis was estimated by calculations based on the data reported in the preceded paper (Yurinskaya et al., 2010). It is found that cell shrinkage and the shift in ion balance in U937 cells induced to apoptosis with 1 μM staurosporine occur due to the coupling of reduced pump activity with a decrease in the integral permeability of Na⁺ channels, whereas K⁺ and Cl⁻ channel permeability remains almost unchanged. Calculations show that only a small part of the total fluxes of K⁺, Na⁺, and Cl⁻ account for the fluxes mediated by NKCC and NC cotransporters. Despite the importance of cotransport fluxes for maintaining the nonequilibrium steady-state distribution of Cl⁻, they cannot play a significant role in apoptotic cell shrinkage because of their minority and cannot be revealed by inhibitors.     

DnaK-dependent ribosome biogenesis in Escherichia coli? : competition for dominance between the alleles dnaK756 and dnaK ?+

The Escherichia coli chaperone DnaK is vital for many cellular functions, including ribosome biogenesis at high temperature. Thus, the dnaK756-ts (λ ^R ) mutant, at the non-permissive temperature, is inhibited at a late stage of ribosome assembly, yielding 21S, 32S and 45S precursor particles. This defect, unlike the λ resistance and thermosensitivity phenotypes, is not complemented by lysogenisation with a transducing phage λ dnaK ⁺ bearing the wild-type dnaK gene. However this dominant phenotype becomes recessive when dnaK ⁺ is expressed from a medium-copy-number plasmid. On the other hand, an excess of DnaK causes an unexpected dominant-lethal effect of the dnaK756 allele near non-permissive temperatures. This interplay between the dnaK ⁺ and dnaK756 alleles supports the idea of that DnaK oligomers form in the cell. Received: 28 April 1998 / Accepted: 24 July 1998     

A comparative study of the mechanism of Na+ and Cl? excretion by the gill ofMugil capito andFundulus heteroclitus: Effects of Stress

Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na⁺ and of Cl^– and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not . InFundulus, is also decreased. Transfer of the two species from SW to fresh water (FW) reduces and by 75 to 85% and leads to a large inversion of P.D. When K⁺ is added to FW, a gill depolarization occurs, as well as a large increase of and .These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na⁺ ( ) being greater than that to Cl^– ( ), 2) a Cl^–/Cl^– exchange independent of P.D. is associated with the Cl^– pump; 3) Cl^– pump activity is linked to Na⁺/K⁺ exchange which in turn is associated to a Na⁺/Na⁺ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of and observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of which becomes equal to in both species.As a result of stress, the K⁺-activated Na⁺ and Cl^– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil.     

KcsA 通道对Na+、K+及Rb+离子选择性的统计热力学研究

钾离子的通透率至少比钠离子的通透率大10000倍,这个问题至今没有很好地解决.为了在分子水平阐释钾离子通道的选择性机制,以KcsA钾通道X射线衍射结构为基础,采用密度泛函理论计算了不同离子在离子通道中的位能.计算结果表明,Rb+离子具有与K+离子相类似的位能曲线,但是其在通透过程遇到的位垒要比K+离子的位垒高,因而所对应的通透率也就小于钾离子的通透率,而钠离子的的通透率仅仅是钾离子通透率的0.0067%.文中所涉及的系统仅仅包含269个原子,而用分子动力学虽然也可以得到相近的结果,但是它的系统大小为41 000个原子.     

梭梭Na+/H+逆向转运蛋白基因克隆及分析

采用RT-PCR、RACE方法从超旱生、耐盐植物梭梭中扩增出Na+/H+逆向转运蛋白基因的开放阅读框架,其核苷酸序列长1 683bp,推测的氨基酸序列全长为560个氨基酸残基。含有多个物种Na+/H+逆向转运蛋白基因的高度保守序列氨氯砒嗪脒的结合位点(LFFIYLIPPI)。序列一致性分析结果显示,该cDNA片段与同科植物NHX基因的一致性为70%～80%,但与不同科植物的一致性较低,仅为60%,表明该基因在进化上存在多样性,但它们都具有氨氯砒嗪脒结合位点,对Na+具有高度专一性,对植物的耐盐性起着重要作用。     

Electrically silent cotransport of Na+, K+ and Cl− in ehrlich cells

A cotransport system for Na⁺, K⁺ and Cl^? in Ehrlich cells is described. It is insensitive towards ouabain but specifically inhibited by furosemide and other ‘high ceiling’ diuretics at concentrations which do not affect other pathways of the ions concerned. As the furosemide-sensitive fluxes of these ions are not affected by changes in membrane potential, and as their complete inhibition by furosemide does not appreciably alter the membrane potential, they appear to be electrically silent. Application of the pulse-response methods in terms of irreversible thermodynamics reveals tight coupling between the furosemide-sensitive flows of Na⁺, K⁺ and Cl^? ($\text{q}$ close to unity for all three combinations) at a stoichiometry of 1 : 1 : 2. The site for each of the ions appears to be rather specific: K⁺ can be replaced by Rb⁺ but not by other cations tested whereas Cl^? can be poorly replaced by Br^? but not by NO₃^?, in contradistinction to the Cl^?-OH^? exchange system. The cotransport system appears to function in cell volume regulation as it tends to make the cell swell, thus counteracting the shrinking effect of the ouabain-sensitive (Na⁺, K⁺) pump.The experiments presented could not clarify whether the cotransport process is a primary or secondary active one; while incongruence between transport and conjugated driving force seems to indicate primary active transport, it is very unlikely that hydrolysis of ATP supplies energy for the transport process, since there is no stimulation of ATP turnover observable under operation of the cotransport system.     

Measurements of the gas temperature in an oxygen plasma by spectroscopy of the O2( b 1Σ g+ ) → O2( X 3Σ g? ) transition

A method for measuring the gas temperature in an oxygen plasma by spectroscopy of the electronic transition from the O₂(b ¹Σ _g ⁺ , v = 0) metastable state of molecular oxygen into the O₂(X ³Σ _g ⁻ , v = 0) ground state is considered in detail. The method is verified experimentally for the plasma of dc glow discharge in pure oxygen. It is shown that the gas temperature can be determined by analyzing high-resolution spectra of the P branch of this transition, no matter whether its fine structure (^P P and ^P Q branches) is resolved or masked, provided that the rotational structure of the spectrum is resolved. The feasibility of the method proposed in 1999 by P. Maco and P. Veis for determining the gas temperature from the ratio between the intensity maxima of the R and P branches of the O₂(b ¹Σ _g ⁺ , v = 0) → O₂(X ³Σ _g ⁻ , v = 0) transition in a poorly resolved spectrum was studied experimentally. It is shown that, in order to use this method, it is necessary to know the spectrograph instrumental function. The effect of the spatial inhomogeneity of the temperature and concentration of O₂(b ¹Σ _g ⁺ ) molecules on the accuracy of integral (over the plasma volume) measurements of the gas temperature is investigated using spatially resolved spectroscopy of the O₂(b ¹Σ _g ⁺ , v = 0) → O₂(X ³Σ _g ⁻ , v = 0) transition. It is shown that precise measurements of the temperature require that the optical measurement system be thoroughly adjusted in order for the temperature and concentration of the emitting particles to vary insignificantly over the optically selected volume. Original Russian Text ? S.M. Zyryanov, D.V. Lopaev, 2007, published in Fizika Plazmy, 2007, Vol. 33, No. 6, pp. 563–574.     

Effects of cytochalasin B on water, Na+ and Cl? exchanges in the gill of seawater adapted mulletMugil capito

Summary Electron microscopy study shows that cytochalasin treatment of the mullet damages the microfilaments system in the apex of gill ionocytes: the microfilaments are reduced in number and shortened. Cytochalasin causes a reduction of transgill potential difference and an increase of the Na⁺ and Cl^– blood concentration, of the diffusional water permeability of the gill, of the Na⁺ branchial influx and of Cl^– efflux. The increase of the Na⁺ influx may result in a reduction of the Na⁺ net excretion flux compared to the control. The increased permeability in cytochalasin treated fish facilitates the Cl^– entry probably leading to a reduction of the net Cl^– excretion. The partial inhibition of the K⁺ dependent components of Na⁺ and Cl^– effluxes also contributes to the reduction of Na⁺ and Cl^– excretion. The role of microfilaments in the mechanisms of ionic excretion by the gill is discussed.     

Restoration by the rac locus of recombinant forming ability in recB? and recC? merozygotes of Escherichia coli K-12

Summary The recombinant forming ability of recB ^– or recC ^– strains of E. coli K12 is almost totally recovered in merozygotes which are heterozygous for a genetic locus denoted rac which is located five minutes clockwise from trp on the genetic map. This transient recovery phenomenon only occurs when the donor strain is rac ⁺ (wild type) and the recipient strain is rac ^-. The recombinants derived from such crosses all have the normal phenotype characteristic of recB ^– (or recC ^–) strains, and they are almost always rac ^-. The results imply that the rac ⁺ locus (or loci) is zygotically expressed and excised from the chromosome in a manner which is analogous to the zygotic induction of a prophage.     

Ethanol-hypersensitive and ethanol-dependent cdc? mutants in Schizosaccharomyces pombe

Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc ^– mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc ^– mutants were tested for their ethanol sensitivity; among them, cdc1–7 and cdc13–117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34^cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc ^– phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1 ⁺ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent.     

Fe2+、Cu2+、Zn2+对植物生理特性影响的比较分析

以浸水处理为对照系统分析了Fe2+、Cu2+、Zn2+等金属离子对植物胁迫损伤相关的7个生理指标,并应用数理统计学和生物化学的相关原理和方法从氧自由基伤害的角度比较分析了这三种离子处理对植物生理特性的影响。结果表明:不同离子处理由于对植物造成的胁迫损伤不同,因而它们对植物生理特性的影响效应也有明显差异,并且这种差异与其所处理的离子胁迫性质间存在显著的关联性。     

Pb2+、Cd2+和Ce3+对猪胰α-淀粉酶活性的影响

分别研究了Pb²⁺、Cd²⁺和Ce³⁺对Ca(Ⅱ) α-淀粉酶活性影响及对其Ca²⁺的竞争作用.结果表明三种金属离子低浓度情况下（0.5～5 mmol/L）对α-淀粉酶具有激活现象,而较高浓度则抑制酶活力.Pb²⁺、Cd²⁺和Ce³⁺竞争置换α-淀粉酶中Ca²⁺能力的大小是：Pb²⁺＞Cd²⁺＞Ce³⁺,其抑制酶活作用大小：Pb²⁺＞Cd²⁺＞Ce³⁺.     

川楝素对K+、Ca2+通道活动及细胞内Ca2+浓度的调控

川楝素是我国学者从驱蛔中药中分离、鉴定的一个三萜化合物，已证明具选择地影响神经递质释放，有效地对抗肉毒中毒，促进细胞分化、凋亡，抑制肿瘤增殖，抑制昆虫发育和取食，影响K⁺、Ca²⁺通道活动等多种生物效应. 综述了证明川楝素抑制多种K⁺通道，选择地易化L型Ca²⁺通道和进而升高胞内Ca⁺浓度的研究资料，并对川楝素产生这些生物效应的机制进行了讨论.     

NaHCO3胁迫下3种灌木Na+、K+、Ca2+的吸收及转运

通过盆栽试验,采用原子吸收分光光度法和非损伤微测技术,研究了NaHCO₃胁迫(300 mmol·L^-1)对大洋洲滨藜、四翅滨藜和宁夏枸杞3种灌木离子吸收及运转的影响.结果表明: 随着NaHCO₃浓度升高,两种滨藜和宁夏枸杞叶片中Na⁺含量升高,300 mmol·L^-1NaHCO₃胁迫下,宁夏枸杞叶肉细胞Na⁺的外排增加,两种滨藜净Na⁺外排降低;随着胁迫时间的延长,大洋洲滨藜和宁夏枸杞叶片的K⁺含量下降,Na⁺/K⁺升高,四翅滨藜叶片K⁺含量升高,Na⁺/K⁺降低;随着浓度的升高,宁夏枸杞叶片积累Ca²⁺减少,Na⁺/Ca²⁺高于对照,叶肉细胞Ca²⁺外排;两种滨藜叶Ca²⁺含量总体呈升高趋势,叶肉细胞Ca²⁺表现为内流.在NaHCO₃胁迫下,3种灌木通过不同的策略来消除Na⁺毒害.宁夏枸杞叶片Na⁺的积累抑制了对Ca²⁺的吸收;两种滨藜Ca²⁺的内流促使细胞质中游离Ca²⁺增加,增加的细胞质\[Ca²⁺\]cyt防治质膜H⁺ ATPase去极化,限制K⁺的外排,从而维持细胞内Na⁺/K⁺的平衡,其中四翅滨藜调控Na⁺/K⁺平衡的能力较强.     

胃(H++K+)-ATPase结构与功能的研究

胃(H⁺+K⁺)-ATPase属于生物膜的第二类质子泵(E₁E₂型),从生理角度它是胃酸分泌的质子泵。本文结合我们初步的研究结果:猪、大白鼠胃粘膜(H⁺+K⁺)-ATPase的纯化以及由消炎痛引起的急性胃粘膜病变与胃粘膜(H⁺+K⁺)-ATPase的关系等,对此酶在近十几年来它的纯化、结构、性质、催化机理,向胃腔分泌盐酸的功能及其调节和胃病变的分子机理等方面进行了简要的综述。     

Ca2+-dependent inhibitory effects of Na+ and K− on Ca2+ transport in sarcoplasmic reticulum vesicles

Effects of Na⁺ and K⁺ on Ca²⁺ transport by sarcoplasmic reticulum vesicles were studied in a medium containing high Mg²⁺ and ATP (2mM) and low Ca²⁺ (0.44μM) concentrations. Under these conditions, Na⁺ and K⁺ inhibit Ca²⁺ uptake. ATPase activity and membrane phosphorylation by ATP. Since the concentrations of ATP and Ca²⁺ used are consistent with relaxation in vivo, the results suggest that under physiological resting conditions the Ca²⁺ pump of the sarcoplasmic reticulum operates below its maximal capacity.