超表达AVP1基因提高甜菜的耐低磷和耐盐抗旱性

为探讨H⁺-焦磷酸酶编码基因对甜菜磷吸收和抗性的影响,实现优良基因在甜菜基因工程中的利用,研究在甜菜中超表达拟南芥液泡膜H⁺-焦磷酸酶编码基因AVP1,对转基因甜菜分析其耐低磷、耐盐性和抗旱性。结果显示,AVP1基因在甜菜植株的叶片和块根中表达,且在逆境胁迫下增强表达量响应胁迫;低磷处理条件下,转基因甜菜与野生型甜菜相比具有更高的含磷量,可提高甜菜对磷的吸收利用效率;干旱、盐胁迫处理条件下,AVP1基因在转基因甜菜中显著上升,在盐胁迫或干旱处理条件下,转基因植株的生长受抑程度相对较轻。随着盐和干旱胁迫的加剧,转基因植株体内MDA含量与野生型植株相比较低而脯氨酸含量显著增加,AVP1基因可通过减轻逆境对甜菜细胞膜的损伤及提高甜菜细胞的渗透调节能力,进而增强甜菜对高盐和干旱胁迫的抗性。     

Enhanced drought resistance in fructan-producing sugar beet

Fructans are soluble polymers of fructose that are produced by approximately 15 % of the flowering plant species. Production of bacterial fructans in tobacco has been shown previously to lead to improved biomass production under polyethylene glycol-mediated drought stress. Here, we used the same SacB gene from Bacillus subtilis to produce bacterial fructans in sugar beet (Beta vulgaris L.). The transgenic sugar beets accumulated fructans to low levels (max. 0.5 % of dry weight) in both roots and shoots. Two independent transgenic lines of fructan-producing sugar beets showed significantly better growth under drought stress than untransformed beets. Drought stressed fructan-producing plants attained higher total dry weights (+25–35 %) than wildtype sugar beet, due to higher biomass production of leaves (+30–33 %), storage roots (+16–33 %) and fibrous roots (+37–60 %). Under well-watered conditions, no significant differences were observed between the transgenic and wildtype beets. In conclusion, the introduction of fructan biosynthesis in transgenic plants is a promising approach to improve crop productivity under drought stress.     

Proteome analysis of potato under salt stress

Because salt stress is a major abiotic source of stress on potato crops, the molecular mechanism of the response of potato plants to salt stress was examined. On exposure to salt, the salt-sensitive cultivar Concord showed a greater reduction in shoot and root length than did the salt-tolerant cultivar Kennebec. For both cultivars, the reduction in the length of shoots was more severe than that of the roots. Salt exposure increased the content of free proline and total soluble sugars in shoots of Kennebec; these remained unchanged in Concord. Proteins extracted from shoots of both cultivars exposed to 90 mM NaCl were separated by two-dimensional polyacrylamide gel electrophoresis: 322 and 305 proteins were detected in shoots of Kennebec and Concord, respectively. Of these, 47 proteins were differentially expressed under NaCl treatment in shoot of both cultivars. Among the differentially expressed proteins, photosynthesis- and protein-synthesis-related proteins were drastically down-regulated, whereas osmotine-like proteins, TSI-1 protein, heat-shock proteins, protein inhibitors, calreticulin, and five novel proteins were markedly up-regulated. These results suggest that up-regulation of defense-associated proteins may confer relative salt tolerance to potato plants.     

Penconazole induced changes in photosynthesis, ion acquisition and protein profile of Mentha pulegium L. under drought stress

Effect of penconazole (PEN) treatment on drought-stressed Mentha pulegium L. plants was investigated. Six weeks after sowing, seedlings were grown under soil moisture corresponding to 100, 75, 50 and 25 % field capacity (FC) with or without PEN (15 mg l⁻¹) for 4 weeks. Results showed that the seedlings at 75 % FC showed maximum growth and water supply lower than 75 % FC was the threshold of drought-initiated negative effects on seedling growth. Drought stress significantly induced proline and carbohydrate contents and the decreased chlorophyll, photosynthesis parameters, soluble proteins and ion accumulations. Exogenous PEN increased the growth parameters, pigments, photosynthesis and ion accumulations in drought stressed and unstressed plants, but the effects of PEN were more significant under water deficit conditions. PEN also reduced the negative effects of drought by osmotic balance and protein accumulations. Electrophoretic patterns indicated that PEN treatment increased the intensity of some protein bands with the molecular weights of 30 kDa in shoot and 31 kDa in roots, and several new protein bands with the molecular masses between 116 and 14 kDa appeared in leaves, shoots and roots. These results suggest that the PEN application can be a useful tool in alleviation of effects of drought stress in M. pulegium plants.     

Differences in salt tolerance of three sugar beet genotypes

The effect of increasing NaCl concentrations (up to 150 m M ) on growth and mineral composition of three genotypes of sugar beet ( Beta vulgaris L., MONOHILL, ADA and FIA) has been studied. Growth was stimulated or little affected in water culture by 50 m M NaCl in all 3 genotypes. Further increase in NaCl concentration depressed growth in ADA more than in MONOHILL, whereas in FIA growth did not significantly differ from the untreated control. In all 3 genotypes, particularly in FIA, increasing NaCl concentrations decreased potassium content in the shoots more than in the fibrous and storage roots. Simultaneously, the accumulation of sodium and chloride in the shoots was considerably higher in FIA than in ADA, where in contrast larger proportions of these ions were retained in the roots. The results demonstrate considerable genotypic differences in salt tolerance of sugar beet and indicate a positive correlation between salt tolerance and accumulation of sodium and chloride in the shoots. FIA but not ADA may be suited for a breeding programme of sugar beet for improved salt tolerance.     

植物盐胁迫应答蛋白质组学分析

土壤盐渍化是限制植物生长和分布的关键因素之一,揭示植物盐胁迫应答的分子机理是借助分子生物学手段提高植物耐盐性的基础.近年来,人们利用高通量蛋白质组学技术分析了拟南芥、水稻等19种植物的盐胁迫应答蛋白质表达图谱.从植物类群(盐生植物和甜土植物)、组织器官(根、地上部分/茎、胚根和胚轴、叶片、花序和配子体)、细胞(悬浮培养细胞、愈伤组织细胞和单细胞生物)和亚细胞结构(叶绿体、质膜和质外体)几方面整合分析了植物盐胁迫应答蛋白质组表达模式特征,主要特征包括:(1)盐生植物通过全面调节细胞骨架重塑、离子转运和区隔化、渗透平衡、活性氧(ROS)清除、信号转导、光合作用和能量代谢等信号与代谢网络体系,获得相对较高的抗/耐盐能力;(2)植物地上部分(叶片、茎、配子体)或光合组织细胞(悬浮培养细胞、愈伤组织细胞和单细胞盐藻)通过调节参与光合作用、碳和能量代谢、ROS清除过程蛋白质的表达模式应对盐胁迫环境;(3)植物地下部分(根、胚根)通过调控信号转导和离子转运相关蛋白质感知/传递盐胁迫信号并维持离子平衡;(4)花序中参与渗透调节、转录调控、蛋白质加工和ROS清除的蛋白质在盐胁迫条件下变化显著;(5)叶绿体通过调控参与光合作用、蛋白质加工和周转,以及氧化还原系统平衡等过程应对盐胁迫;(6)质外体中参与细胞壁代谢、胁迫防御和信号转导过程的蛋白质受盐胁迫影响明显;(7)细胞膜中参与维持膜结构稳定、物质/离子运输和信号转导过程的蛋白质对植物盐胁迫应答具有重要作用.这些分析为深入研究植物耐盐的分子机制提供了重要信息.     

盐胁迫对2种栎树苗期生长和根系生长发育的影响

以低浓度(50 mmol/L)和高浓度(150 mmol/L)NaCl处理弗吉尼亚栎(Quercus virginiana)和麻栎(Quercus acutissima)1年生幼苗,研究了2种栎树在盐胁迫下的生长、对盐分的敏感性和耐受性及其根系形态学参数变化以及根系对盐离子的吸收与积累。结果表明,高浓度盐胁迫明显抑制了2种栎树地上部生物量的积累(P0.05),而低浓度盐胁迫对弗吉尼亚栎地上部干重的影响不明显,但显著抑制了麻栎地上部干重(P0.05);2种栎树的根冠比在盐胁迫下呈增加趋势,特别是在高浓度盐胁迫下,2种栎树的根冠比明显增加(P0.05),盐胁迫下增加生物量在根部的分配是植物应对盐胁迫的方式之一。2种栎树根部生物量积累在盐胁迫下变化不明显,但2种栎树根系形态学参数在盐胁迫下的响应不同,弗吉尼亚栎根系总长度、总表面积和总体积在盐胁迫下均有不同程度增加,特别是在低浓度盐胁迫下,根系形态学参数明显增加(P0.05),但麻栎根系形态学参数有下降趋势,但与对照相比变化不明显;通过对不同径级根系总长的分析发现,弗吉尼亚栎根系总长度的增加主要是由于直径小于2 mm的细根总长的增加,细根长度的增加对于植物吸收水分和营养物质具有重要意义;通过对Na+和Cl-在根系的含量分析表明,盐胁迫下2种栎树根系盐离子的积累均有明显增加,但弗吉尼亚栎根系盐离子的含量在低浓度和高浓度盐胁迫下的差异不明显,而麻栎在高浓度盐胁迫下根系盐离子的含量明显高于弗吉尼亚栎。综合2种栎树盐胁迫下的生物量分配策略和根系形态学响应以及盐离子的积累规律,证明2种栎树尽管在生物量分配策略方面具有相同的特点,但根系的响应策略截然不同,弗吉尼亚栎在盐胁迫下能够扩大根系吸收范围,维持较高的K+/Na+比值,而麻栎在盐胁迫下根系由于吸收过多的盐离子,导致根系的生长发育受到抑制,影响了根系在逆境中的分布范围,从而在一定程度上避免了进一步的盐害。     

Physiology and proteome responses of two contrasting rice mutants and their wild type parent under salt stress conditions at the vegetative stage

Salinity is one of the major environmental limiting factors that affects growth and productivity of rice (Oryza sativa L.) worldwide. Rice is among the most sensitive crops to salinity, especially at early vegetative stages. In order to get a better understanding of molecular pathways affected in rice mutants showing contrasting responses to salinity, we exploited the power of 2-DE based proteomics to explore the proteome changes associated with salt stress response. Our physiological observations showed that standard evaluation system (SES) scores, Na⁺ and K⁺ concentrations in shoots and Na⁺/K⁺ ratio were significantly different in contrasting mutants under salt stress condition. Proteomics analysis showed that, out of 854 protein spots which were reproducibly detected, 67 protein spots showed significant responses to salt stress. The tandem mass spectrometry analysis of these significantly differentially accumulated proteins resulted in identification of 34 unique proteins. These proteins are involved in various molecular processes including defense to oxidative stresses, metabolisms, photosynthesis, protein synthesis and processing, signal transduction. Several of the identified proteins were emerged as key participants in salt stress tolerance. The possible implication of salt responsive proteins in plant adaptation to salt stress is discussed.     

Proteome Dynamics and Physiological Responses to Short-Term Salt Stress in Brassica napus Leaves

Salt stress limits plant growth and crop productivity and is an increasing threat to agriculture worldwide. In this study, proteomic and physiological responses of Brassica napus leaves under salt stress were investigated. Seedlings under salt treatment showed growth inhibition and photosynthesis reduction. A comparative proteomic analysis of seedling leaves exposed to 200 mM NaCl for 24 h, 48 h and 72 h was conducted. Forty-four protein spots were differentially accumulated upon NaCl treatment and 42 of them were identified, including several novel salt-responsive proteins. To determine the functional roles of these proteins in salt adaptation, their dynamic changes in abundance were analyzed. The results suggested that the up-accumulated proteins, which were associated with protein metabolism, damage repair and defense response, might contribute to the alleviation of the deleterious effect of salt stress on chlorophyll biosynthesis, photosynthesis, energy synthesis and respiration in Brassica napus leaves. This study will lead to a better understanding of the molecular basis of salt stress adaptation in Brassica napus and provides a basis for genetic engineering of plants with improved salt tolerance in the future.     

Biosynthesis, translocation, and accumulation of betaine in sugar beet and its progenitors in relation to salinity

Like other halophytic chenopods, sugar beet (Beta vulgaris L.) can accumulate high betaine levels in shoots and roots. N,N,N-trimethylglycine impedes sucrose crystallization and so lowers beet quality. The objective of this research was to examine the genetic variability and physiological significance of betaine accumulation in sugar beet and its relatives. Three cultivated genotypes of B. vulgaris and two genotypes of the wild progenitor B. maritima L. were grown with and without gradual salinization (final NaCl concentration = 150 millimolar). At 6 weeks old, all five genotypes had moderately high betaine levels in shoots and roots when unsalinized (averages for all genotypes: shoots = 108 micromoles per gram dry weight; roots = 99 micromoles per gram dry weight). Salinization raised betaine levels of shoots and roots 2- to 3-fold, but did not greatly depress shoot or root growth. The genotype WB-167—an annual B. maritima type—always had approximately 40% lower betaine levels in roots than the other four genotypes, although the betaine levels in the shoots were not atypically low.

The site and pathway of betaine synthesis were investigated in young, salinized sugar beet plants by: (a) supplying 1 micromole [¹⁴C]ethanolamine to young leaf blades or to the taproot sink of intact plants; (b) supplying tracer [¹⁴C]formate to discs of leaf, hypocotyl, and taproot tissues in darkness. Conversion of both ¹⁴C precursors to betaine was active only in leaf tissue. Very little ¹⁴C appeared in the phospholipid phosphatidylcholine before betaine was heavily labeled; this was in marked contrast to the labeling patterns in salinized barley. Phosphorylcholine was a prominent early ¹⁴C metabolite of both [¹⁴C]ethanolamine and [¹⁴C]formate in all tissues of sugar beet. Betaine translocation was examined in young plants of sugar beet and WB-167 by applying tracer [methyl-¹⁴C]betaine to a young expanded leaf and determining the distribution of ¹⁴C after 3 days. In all cases, extensive ¹⁴C translocation to young leaves and taproot sink occurred; neither in the fed leaf nor in sink organs were any ¹⁴C metabolites of betaine detected.

     

Abscisic acid root and leaf concentration in relation to biomass partitioning in salinized tomato plants

Salinization is one of the most important causes of crop productivity reduction in many areas of the world. Mechanisms that control leaf growth and shoot development under the osmotic phase of salinity are still obscure, and opinions differ regarding the Abscisic acid (ABA) role in regulation of biomass allocation under salt stress. ABA concentration in roots and leaves was analyzed in a genotype of processing tomato under two increasing levels of salinity stress for five weeks: 100 mM NaCl (S10) and 150 mM NaCl (S15), to study the effect of ABA changes on leaf gas exchange and dry matter partitioning of this crop under salinity conditions. In S15, salinization decreased dry matter by 78% and induced significant increases of Na⁺ and Cl⁻ in both leaves and roots. Dry matter allocated in different parts of plant was significantly different in salt-stressed treatments, as salinization increased root/shoot ratio 2-fold in S15 and 3-fold in S15 compared to the control. Total leaf water potential (Ψ_w) decreased from an average value of approximately −1.0 MPa, measured on control plants and S10, to −1.17 MPa in S15. In S15, photosynthesis was reduced by 23% and stomatal conductance decreased by 61%. Moreover, salinity induced ABA accumulation both in tomato leaves and roots of the more stressed treatment (S15), where ABA level was higher in roots than in leaves (550 and 312 ng g⁻¹ fresh weight, respectively). Our results suggest that the dynamics of ABA and ion accumulation in tomato leaves significantly affected both growth and gas exchange-related parameters in tomato. In particular, ABA appeared to be involved in the tomato salinity response and could play an important role in dry matter partitioning between roots and shoots of tomato plants subjected to salt stress.     

Does Inoculation with Glomus mosseae Improve Salt Tolerance in Pepper Plants?

A pot experiment was conducted to determine the effects of Glomus mosseae inoculation on growth and some biochemical activities in roots and shoots of pepper (Capsicum annuum L. cv. Zhongjiao 105) plants subjected to four levels of NaCl [0 (control), 25 (low), 50 (medium), and 100 (high) mM] for 30 days, after 30 days of establishment under non-saline conditions. In mycorrhizal (M) plants, root colonization varied from 48 to 16 %. M plants had higher root and shoot dry weight and leaf area compared with non-mycorrhizal (NM) plants. Under salinity stress, M plants accumulated higher amounts of leaf photosynthetic pigments as well as soluble sugar, soluble protein, and total free amino acids in roots and shoots than those of NM plants. In contrast, the accumulation of proline was less intense in M plants than NM plants. Salt stress induced oxidative stress by increasing malondialdehyde (MDA) content; however, the extent of oxidative damage in M plants was less compared with NM plants due to G. mosseae-enhanced activity of superoxide dismutase (SOD) and peroxidase (POD). We concluded that inoculation with G. mosseae improved growth performance and enhanced salt tolerance of pepper plants via improving photosynthetic pigments and the accumulation of organic solutes (except proline), reducing oxidative stress, and enhancing antioxidant activities of the SOD-POD system.     

Regulation of protein synthesis in root, shoot and embryonic tissues of germinating barley during salinity stress

Abstract Protein synthesis during seed germination, a stage vulnerable to salinity stress, was investigated. The responses of barley genotypes, CM72 (California Mariout 72) and Prato, toward salinity were different during seed germination. Germination of CM72 was unaffected up to 0.34 kmol m^?3 (2%) NaCl, but that of Prato was reduced 30% by 0.17 kmol m ³ NaCl and 75% by 0.34 kmol m^?3 NaCl. Therefore, the former genotype is relatively more salt-tolerant than the latter. Protein synthesis in roots, shoots, and embryos was investigated in these two genotypes before and after salinity stress. The uptake of S-methionine and its incorporation into protein were significantly reduced by salinity in both genotypes. The inhibition of global protein synthesis was significant in roots and shoots. Proteins from different tissues were resolved by single and two dimensional gels. The steady-state protein levels were maintained remarkably well during salinity stress in roots and shoots. Likewise, proteins in germinating embryos were stable except for a 42-kilodalton protein unique to the salt tolerant genotype which was apparently degraded during salinity stress. Salinity, around 0.34 kmol m^?3 NaCl, induced both quantitative and qualitative changes in the expression of some proteins labelled in vivo. The quantitative changes included repression or enhancement of synthesis of selected groups of proteins. Around 8% of the nearly 400 resolved proteins in a tissue was affected this way. Some of the proteins in this category were specific to each genotype. About 1 % of the total showed qualitative changes; these proteins were expressed only during salinity stress. In roots, two proteins (28, 41.7 kilodaltons) were detected in CM72 and five (28, 45, 60.5, 76.5, 82.5 kilodaltons) in Prato; only the 28-kilodalton protein was common to both genotypes. In shoots, four proteins (45, 60.5, 76.5, 82.5 kilodaltons) were found only in Prato and these were similar to those induced in roots. The four new proteins (32, 37.5, 89, 92 kilodaltons) in germinating embryos were apparently induced only in CM72; these were distinctly different from those detected in developed roots and shoots. The unique protein changes induced by salinity stress during germination (this study) and seedling growth studies reported earlier (Ramagopal, 1987b) are apparently different. The findings demonstrate that ontogeny plays an important role in the expression of tissue-specific proteins during salinity stress in the salt tolerant and sensitive barley genotypes.