Salicylic acid-induced adaptive response to copper stress in sunflower (Helianthus annuus L.)

The ameliorative effect of salicylic acid (SA: 0.5 mM) on sunflower (Helianthus annuus L.) under Cu stress (5 mg l⁻¹) was studied. Excess Cu reduced the fresh and dry weights of different organs (roots, stems and leaves) and photosynthetic pigments (chlorophyll a, b and carotenoids) in four-week-old plants. There was a considerable increase in Chl a/b ratio and lipid peroxidation in both the roots and leaves of plants under excess Cu. Soluble sugars and free amino acids in the roots also decreased under Cu stress. However, soluble sugars in the leaves, free amino acids in the stems and leaves, and proline content in all plant organs increased in response to Cu toxicity. Salicylic acid (SA) significantly reduced the Chl a/b ratio and the level of lipid peroxidation in Cu-stressed plants. Under excess Cu, a higher accumulation of soluble sugars, soluble proteins and free amino acids including proline occurred in plants treated with 0.5 mM SA. Exogenous application of SA appeared to induce an adaptive response to Cu toxicity including the accumulation of organic solutes leading to protective reactions to the photosynthetic pigments and a reduction in membrane damage in sunflower.     

Alleviation of Changes in Protein Metabolism in NaCl-Stressed Wheat Seedlings by Thiamine

NaCl-stress induced a pronounced suppression in growth of wheat seedlings. The most abundant amino acids (cysteine, arginine, methionine) constituting about 55 % of total free amino acid content in control wheat were reduced in 100 mM NaCl-treated plants. However, valine, isoleucine, aspartic acid and proline accumulated in response to NaCl stress and NaCl-treated wheat seedlings showed 1.6 fold increase in total free amino acids compared to the control. Addition of 2 [micro ]M thiamine alleviated the effects of NaCl on the amino acid composition and the amount of total free amino acids decreased to that in the control. Content of 26 kDa protein increased in NaCl-treated plants, stimulation was more pronounced in roots than in shoots. In contrast, the contents of 13 and 20 kDa proteins decreased. After addition of thiamine, the 24 kDa protein, which disappeared with NaCl treatment, has been initiated again. Moreover, thiamine treatment stimulated the accumulation of the 20 kDa protein.     

Accumulation of proline and glycine betaine in Ipomoea pes-caprae induced by NaCl

The present study pertains to the effect of different concentration of NaCl on the contents of proteins, free amino acids, proline and glycine betaine in leaves, stems and roots of Ipomoea pes-caprae. The protein content of the tissues increased in response to salinity upto 200 mM NaCl; the free amino acids content showed a reversal trend. The proline and glycine betaine contents increased with increasing salinity upto 500 mM NaCl. The accumulation of proline and glycine betaine might play a role in the alleviation of salt stress. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of Water Stress on Water Relations, Photosynthetic Parameters and Nitrogen Metabolism of Moth Bean Genotypes

Effects of water stress at pre-flowering stage were studied in three genotypes (RMO-40, Maru moth and CZM-32 E) of moth bean [Vigna aconitifolia (Jacq.) Marechal]. Increasing water stress progressively decreased plant water potential, leaf area, net photosynthetic rate, starch and soluble protein contents and nitrate reductase activity while contents of reducing sugars, total soluble sugar, free amino acids and free proline progressively increased. Significant genotypic differences were observed and genotype CZM-32-E displayed a better drought tolerance than other genotypes.     

盐碱胁迫下星星草种子萌发过程中氮代谢的初步研究

对不同浓度Ｎａ２ＣＯ３胁迫下星星草种子萌发过程中可溶性蛋白质,游离氨基酸及游离脯氨酸含量的变化进行了研究。结果表明：无盐胁迫下,伴随种子的萌发过程,可溶性蛋白质,游离氨基酸含量不断增加。     

Effects of salinity and heat-shock on wheat seedling growth and content of carbohydrates,proteins and amino acids

The effects of salinity (0, 50, 100, 150, and 200 mM NaCl) and heat-shock (42°C) and their interactions on germination, seedling growth, and some relevant metabolic changes of two cultivars (cv. Giza 155 and cv. Stork) of wheat (Triticum vulgaris L.) were studied. Germination studies indicate that plants tolerated salinity up to 100 mM NaCl. The lengths of roots and shoots and their water content, as well as fresh and dry matter yield of cv. Giza 155 seedlings remained more or less unchanged up to 100 mM NaCl and of cv. Stork up to 50 mM NaCl. Salinity induced progressive increase in soluble carbohydrates, soluble proteins and proline in cv. Giza 155 and in soluble proteins, proline and other free amino acids in cv. Stork. However, under the higher salinity levels, in cv. Giza 155 increase in soluble carbohydrates was accompanied by lose in other free amino acids, whereas in cv. Stork an opposite effect was obtained. Heat-shock treatment (42°C for 24 h) induced a significant decrease in the final germination percentage, the shoot and root lengths, fresh matter yield and the water content. The dry matter yield of the two cultivars was considerably increased as compared with the corresponding treatments with NaCl only. Heat-shock treatment resulted in a significant increase, in the amount of soluble carbohydrates and proline in salt treated seedlings of both cultivars. The pattern of changes in amino acids was opposite to that of soluble proteins, indicating that the increase in soluble proteins was at the expense of other amino acids in cv. Giza 155 andvice versa in cv. Stork.     

Sources of Proline-nitrogen in Water-stressed Soybean (Glycine max L.) I. Protein Metabolism and Proline Accumulation

Water stress was imposed upon soybean plants (Glycine max L.)grown in a greenhouse by withholding irrigation for 10 daysafter 5 weeks of growth, and the changes under stress in thelevels of free amino acids, free ammonia and protein were determinedin detail. With a decrease in the leaf water potential, theprotein content gradually decreased, whereas the free ammoniacontent was relatively constant. Water stress induced an increasein the levels of free amino acids normally present in proteinsuch as isoleucine, leucine, valine, phenylalanine, glutamineand histidine, indicating that protein hydrolysis occurs understress. Proline accumulated only under severe stress (below–1.5 MPa) and attained 0.86% of the dry weight on day10 (–2.6 MPa). Asparagine also accumulated only undersevere stress (below –2.0 MPa). The concentration of glutamicacid, alanine, aspartic acid, serine, glycine and arginine remainedvirtually unchanged during the stress period. Total proline(protein-bound+free) first decreased during mild to moderatestress, and then increased over that of the well-irrigated controlplants at severe stress due to a remarkable accumulation offree proline. These findings indicate that some de novo synthesisof proline occurs under severe stress and that the nitrogensource for this proline synthesis may be protein. (Received July 4, 1981; Accepted September 11, 1981)     

Accumulation of some nitrogen compounds in response to salt stress and their relationships with salt tolerance in rice (Oryza sativa L.) seedlings

The salt-induced accumulation of some nitrogen compounds (free amino acids, ammonium and urea) in shoots of eight rice cultivars differing in salt tolerance was investigated. Salt treatment (100 mM, 6 days) significantly increased the proline content of shoots but this appeared to be a reaction to stress damage and not associated with salt tolerance, because proline contents were higher in the more sensitive cultivars. Besides proline, some other free amino acids also accumulated leading to a significant increase in the total amino acid content of the stressed seedlings. High levels of free ammonium also accumulated under conditions of stress; this was highly correlated with the accumulation of Na⁺ in the shoots and negatively correlated with salt tolerance. The accumulation of ammonium was positively correlated with the accumulation of many free amino acids, and also associated with the production of urea in the stressed seedlings. Results from the present investigations suggest that an increase in the concentration of some free amino acids including proline, may be a result of the reassimilation of the stress-induced ammonium. A high capacity to assimilate ammonium may be an important factor in alleviating the consequence of stress because ammonium can be toxic at high concentrations.     

Dynamic metabonomic responses of tobacco (Nicotiana tabacum) plants to salt stress

Metabolic responses are important for plant adaptation to osmotic stresses. To understand the dosage and duration dependence of salinity effects on plant metabolisms, we analyzed the metabonome of tobacco plants and its dynamic responses to salt treatments using NMR spectroscopy in combination with multivariate data analysis. Our results showed that the tobacco metabonome was dominated by 40 metabolites including organic acids/bases, amino acids, carbohydrates and choline, pyrimidine, and purine metabolites. A dynamic trajectory was clearly observable for the tobacco metabonomic responses to the dosage of salinity. Short-term low-dose salt stress (50 mM NaCl, 1 day) caused metabolic shifts toward gluconeogenesis with depletion of pyrimidine and purine metabolites. Prolonged salinity with high-dose salt (500 mM NaCl) induced progressive accumulation of osmolytes, such as proline and myo-inositol, and changes in GABA shunt. Such treatments also promoted the shikimate-mediated secondary metabolisms with enhanced biosynthesis of aromatic amino acids. Therefore, salinity caused systems alterations in widespread metabolic networks involving transamination, TCA cycle, gluconeogenesis/glycolysis, glutamate-mediated proline biosynthesis, shikimate-mediated secondary metabolisms, and the metabolisms of choline, pyrimidine, and purine. These findings provided new insights for the tobacco metabolic adaptation to salinity and demonstrated the NMR-based metabonomics as a powerful approach for understanding the osmotic effects on plant biochemistry.     

NaCl stress causes changes in photosynthetic pigments,proteins, and other metabolic components in the leaves of a true mangrove,<Emphasis Type="Italic">Bruguiera parviflora</Emphasis>, in hydroponic cultures

We studied salt stress-induced biochemical changes in young, hydroponically grown plants of mangrove,Bruguiera parviflora (Rhizophoraceae). Our focus was on the effect of NaCI (applied at 100, 200, 400, or 500 mM) on leaf pigments, total soluble proteins, total free amino acids, carbohydrates, polyphenols, and proline. The total Chi content increased for 14 d after treatment with 100 mM NaCI, then gradually stabilized. At 400 mM, the total Chi content slowly decreased over the 45-d test period. However, the Chia:b ratio remained unchanged in isolated chloroplasts and in leaf tissue. Percent changes in the carotenoids content followed the same trend as for Chi, except for a 1.5-fold decrease during the 400-mM NaCI treatment, compared with the control. The total sugar content increased by 2.5-fold by Day 45 after treatment with 400 mM NaCI, whereas the starch content measured in the same treatment decreased by 40 to 45%. Leaf protein content decreased as salinity increased, which suggests either a possible disruption in the protein synthesis mechanism or, more likely, an increase in proteolytic activity. The total amino-acid pool increased steadily, by four-fold, in the 45-d, 400-mM treatment Both proline and polyphenols accumulated with increasing levels of salinity, which confirms the role of proline as a stress-induced protective metabolite in the adaptive process of this species. Our results showed that a true mangrove such as 8.parviflora can easily be sustained and propagated under low-salinity conditions. At high levels of salinity (~400 mM, beyond which they could not survive), the plants became adapted to salt stress after two to three weeks. During this adaptive period, changes in pigment and protein levels also occurred. The accumulation of proline and polyphenols played a key role in the plant’s stressinduced adjustment to NaCI under hydroponic culture conditions.     

Physiological effects of exogenous nitric oxide on Brassica juncea seedlings under NaCl stress

The study was conducted to investigate the physiological effects of exogenous NO on potherb mustard (Brassica juncea Coss.) seedlings under salt stress. The plants were grown in Hogland nutrient solution for 15 d and treated with 150 mM NaCl, NO donor sodium nitropruside (SNP) and NO scavenger methylene blue (MB-1) for 4 d. The NaCl stress increased superoxide dismutase, peroxidase and ascorbate peroxidase activities and malondialdehyde (MDA) and free proline contents, and decreased soluble protein content. However, the application of exogenous NO limited the production of MDA and free proline, while markedly promoted SOD, POD and APX activity.     

外源一氧化氮、水杨酸和过氧化氢对烟草叶片游离氨基酸和可溶性蛋白含量的影响

测定了NO、SA和H2O2三种信号分子对烟草氮代谢产物游离氨基酸、脯氨酸和可溶性蛋白质含量的影响。结果表明：NO、SA和H2O2能调节烟草脯氨酸、游离氨基酸和可溶性蛋白质含量。低浓度的NO和H2O2处理后12h能提高脯氨酸含量,而较高浓度的NO、SA和H2O2处理降低烟草脯氨酸和游离氨基酸含量;三者对脯氨酸、游离氨基酸和可溶性蛋白质含量的影响具有相似性。     

Changes in Mulberry Leaf Metabolism in Response to Water Stress

A series of experiments were conducted to characterize the water stress-induced changes in the activities of RuBP carboxylase (RuBPCO) and sucrose phosphate synthase (SPS), photosystem 2 activity, and contents of chlorophylls, carotenoids, starch, sucrose, amino acids, free proline, proteins and nucleic acids in mulberry (Morus alba L. cv. K-2) leaves. Water stress progressively reduced the activities of RuBPCO and SPS in the leaf extracts, the chlorophyll content, and PS2 activity in isolated chloroplasts. Plants exposed to drought showed lower content of starch and sucrose but higher total sugar content than control plants. While the soluble protein content decreased under water stress, the amino acid content increased. Proline accumulation (2.5-fold) was noticed in stressed leaves. A reduction in the contents of DNA and RNA was observed. Reduced nitrogen content was associated with the reduction in nitrate reductase activity. SDS-PAGE protein profile showed few additional proteins (78 and 92 kDa) in the water stressed plants compared to control plants.     

万寿菊属不同品种初花期抗旱特性分析

以万寿菊属(Tagetes)9个品种为试验材料,研究了自然持续干旱胁迫对它们初花期的花最大直径、叶色、旱害指数等形态指标以及叶绿素含量(Chl a+b,Ch a/b)、叶片相对含水量(RWC)、叶片保水力(WHC)、叶片和花的脯氨酸、可溶性糖和可溶性蛋白含量等生理指标的影响,以揭示其抗旱特性及其生理机制.结果显示:(1)持续6d干旱胁迫条件下,万寿菊9个品种花的最大直径显著降低,叶绿素含量和相对含水量均呈明显下降趋势.(2)万寿菊叶片的脯氨酸、可溶性蛋白和可溶性糖含量均呈上升趋势;而花的脯氨酸含量持续上升,可溶性蛋白含量呈下降趋势,但可溶性糖含量变化趋势复杂.(3)万寿菊旱害指数与其叶片相对含水量、叶绿素总含量、叶片和花的脯氨酸含量、叶片可溶性蛋白含量呈极显著相关.研究表明,抗旱性强的品种可以通过调节自身的渗透调节物质含量减轻干旱伤害;9个品种初花期抗旱性强弱依次为:珍妮>金门>鸿运>拳王>巨人>发现>小英雄>大英雄>迪阿哥.     

Counteraction of Salinity Stress on Wheat Plants by Grain Soaking in Ascorbic Acid, Thiamin or Sodium Salicylate

The interactive effects of salinity stress (40, 80, 120 and 160 mM NaCl) and ascorbic acid (0.6 mM), thiamin (0.3 mM) or sodium salicylate (0.6 mM) were studied in wheat (Triticum aestivum L.). The contents of cellulose, lignin of either shoots or roots, pectin of root and soluble sugars of shoots were lowered with the rise of NaCl concentration. On the other hand, the contents of hemicellulose and soluble sugars of roots, starch and soluble proteins of shoots, proline of either shoots or roots, and amino acids of roots were raised. Also, increasing NaCl concentration in the culture media increased Na⁺ and Ca²⁺ accumulation and gradually lowered K⁺ and Mg²⁺ concentration in different organs of wheat plant. Grain soaking in ascorbic acid, thiamin or sodium salicylate could counteract the adverse effects of NaCl salinity on the seedlings of wheat plant by suppression of salt stress induced accumulation of proline.     

Amino acid and protein changes in the haemolymph of developing fourth instar Chironomus tentans

The concentration of free amino acids, total soluble protein, and haemoglobin in the haemolymph of fourth instar Chironomus tentans was investigated.The concentration of the free amino acid pool increases between the early (15.7 mM/l) and mid-(33.9 mM/l) fourth larval stages followed by a decline during the late (16.9 mM/l) fourth larval period. Alanine, serine, and the amides of aspartic acid and glutamic acid are the predominant free amino acids at all stages. Physiological fluid analysis of late fourth instar haemolymph detected 32 ninhydrin positive components including 18 common amino acids plus homoarginine, ornithine, citrulline, β-alanine, α-aminoadipic acid, α-aminoisobutyric acid, and sarcosine.The concentration of total soluble protein steadily increases during fourth instar larval development to a maximum of $\text{9.3}\text{g}\text{100}\text{ml}$ followed by a decline during the pharate pupal period. A similar pattern of variation occurs in haemoglobin content which comprises from 51 to 66% of Chironomus tentans haemolymph protein.The mM percentage of individual amino acids of total haemolymph protein varies little during the fourth instar. At all stages alanine and aspartic acid are the predominant amino acids.     

Biochemical Changes in Terminal Root Galls Caused by an Ectoparasitic Nematode,Longidorus africanus: Amino Acids

The amino acids of terminal root galls caused by Longidorus africanus on bur marigold (Bidens tripartita L.) and grapevine (Vitis vinifera L.) were studied. The galled roots of bur marigold contained 73% more cell-wall protein and 184% more free amino acids. The main changes among the free amino acids of the galled tissue were a large increase (1900%) in proline and a decrease in aspartic acid (56%) compared with the respective check tissue. Hydroxyproline decreased in the wall protein fraction from 5.6% in the healthy tissue to 3.6% in the infected tissue.Percent of hydroxyproline in total amino acids of the wall protein fraction of grapevine roots decreased from 0.7% in the healthy tissue to 0.3% in the galled tissue, and total proteins of this fraction decreased from 9.5 mg to 4.5 rag, respectively. Total protein in the protoplasmic fraction also decreased from 3.0 mg in healthy to 1.0 mg in infected roots. No change was noticed in total proteins in the free amino acids fraction but free proline decreased 40% in the infected roots.The relationship of these differences to the specific reactions of the hosts to nematode feeding is discussed.     

Influence of zinc on soluble carbohydrate and free amino acid levels in rapeseed plants regenerated in vitro in the presence of zinc

To gain more insight into the impact of zinc on the primary metabolites in rapeseed, plants were regenerated in vitro in the presence of zinc (0.1–1 mM), acclimatized, transferred to a greenhouse, and treated with 2 mM ZnSO₄. The main metabolites, including soluble carbohydrates and free amino acids, were analyzed by nuclear magnetic resonance spectroscopy, and further confirmed by spectrophotometry and enzymatic analyses. Exposure of these greenhouse-grown plants to ZnSO₄ led to both a significant rise of the total amino acid level and an increase of proline accumulation in the different tissues. Moreover, the control plants, regenerated without zinc stress, exhibited a significant reduction of soluble carbohydrate levels, whereas the plants derived from Zn-treated regenerants exhibited significantly higher levels of both glucose and sucrose. These levels increased proportionally with the Zn concentration in the regeneration step.     

Proline accumulation and glutamine synthetase activity are increased by salt-induced proteolysis in cashew leaves

In this study cashew (Anacardium occidentale) plants were exposed to a short- and long-term exposure to NaCl in order to establish the importance of the salt-induced proteolysis and the glutamine synthetase activity on the proline accumulation. The cashew leaf showed a prominent proline accumulation in response to salt stress. In contrast, the root tissue had no significant changes in proline content even after the drastic injury caused by salinity on the whole plant. The leaf proline accumulation was correlated to protease activity, accumulation of free amino acid and ammonia, and decrease of both total protein and chlorophyll contents. The leaf GS activity was increased by the salt stress whereas in the roots it was slightly lowered. Although the several amino acids in the soluble pool of leaf tissue have showed an intense increment in its concentrations in the salt-treated plants, proline was the unique to show a proportional increment from 50 to 100 mol m-3 NaCl exposure (16.37 to 34.35 mmol kg-1 DM, respectively). Although the leaf glutamate concentration increased in the leaves of the salt-stressed cashew plants, as compared to control, its relative contribution to the total amino acid decreased significantly in stressed leaves when compared to other amino acids. In addition, when the leaf discs were incubated with NaCl in the presence of exogenous precursors (Glu, Gln, Orn or Arg) involved in the proline synthesis pathways, the glutamate was unique in inducing a significant enhancement of the proline accumulation compared to those discs with precursor in the absence of NaCl. These results, together with the salt-induced increase in the GS activity, suggest an increase in the de novo synthesis of proline probably associated with the increase of the concentration of glutamate. Moreover, the prominent salt-induced proline accumulation in the leaves was associated with the higher salt-sensitivity in terms of proteolysis and salt-induced senescence as compared to the roots. In conclusion, the leaf-proline accumulation was due, at least in part, to the increase in the salt-induced proteolysis associated with the increments in the GS activity and hence the increase in the concentration of glutamate precursor in the soluble amino acid pool.