Constitutive expression of mustard annexin, <Emphasis Type="Italic">AnnBj1</Emphasis> enhances abiotic stress tolerance and fiber quality in cotton under stress

Annexins belong to a multigene family of Ca²⁺ dependent, phospholipid and cytoskeleton binding proteins. They have been shown to be upregulated under various stress conditions. We generated transgenic cotton plants expressing mustard annexin (AnnBj1), which showed enhanced tolerance towards different abiotic stress treatments like sodium chloride, mannitol, polyethylene glycol and hydrogen peroxide. The tolerance to these treatments was associated with decreased hydrogen peroxide levels and enhanced total peroxidase activity, enhanced content of osmoprotectants- proline and sucrose in transgenic plants. They showed higher retention of total chlorophyll and reduced TBARS in leaf disc assays with stress treatments, and decreased hydrogen peroxide accumulation in the stomatal guard cells when compared to their wild type counterparts. They also showed significantly enhanced fresh weight, relative water content, dry weight under stress. Treatment with sodium chloride resulted in enhanced expression of genes for ∆-pyrroline-5-carboxylase synthetase in leaves, and sucrose phosphate synthase, sucrose synthase and cellulose synthase A in the leaves and fibers of transgenic plants. The transgenic plants maintained normal seed development, fiber quality and cellulose content under stress.     

油菜素内酯对NaCl胁迫下棉花叶片生理特征和基因表达谱的影响

研究了外源油菜素内酯(BL)对NaCl胁迫下棉花幼苗的钠累积、叶片生理特征及叶片差异基因表达水平的影响.结果表明： NaCl胁迫下2个棉花品种各部位钠含量升高,叶片丙二醛(MDA)、脯氨酸含量上升,叶绿素含量下降,叶片基因表达水平受到影响.外源施用油菜素内酯可降低NaCl胁迫下棉花幼苗根、茎、叶的钠含量,降低叶片中MDA含量,提高脯氨酸含量,并且NaCl胁迫下苏棉12号棉花品种更易受油菜素内酯调控.对苏棉12号的叶片进行数字表达谱分析结果表明,NaCl胁迫下苏棉12号叶片中的差异基因表达水平受到油菜素内酯调控,BL+NaCl处理棉花叶片的基因表达模式与CK(正常生长棉株)更为一致.说明外源油菜素内酯可减轻NaCl胁迫下棉花叶片受抑制程度,从而使NaCl胁迫下棉花叶片生理功能增强(叶绿素含量升高),最终使生物量增加.     

蕾期土壤盐度降低后棉花叶片的生理功能恢复

试验于2011—2012年在江苏南京江苏省农业科学院经济作物研究所试验田进行,采用盆栽方法,以鲁棉研37号和苏棉22号为供试材料,设置土壤盐度降低试验(初始土壤含盐量为0.2%,棉花进入二叶期后每7d加入混合盐1次,每次增加0.1%,使土壤含盐量逐渐达到0.5%,蕾期进行盐度降低处理,使土壤含盐量降低到0.2%左右),研究蕾期土壤盐度降低后棉花叶片的生理代谢动态特征。结果表明:土壤盐度降低后,棉花叶片叶绿素(Chl)、类胡萝卜素(Car)含量和Chl/Car升高;净光合速率和气孔导度升高,且分别在土壤盐度降低后第14天和7天接近于低盐对照;土壤盐度降低后棉花叶片超氧化物歧化酶(SOD)和过氧化物酶(POD)活性升高,过氧化氢酶(CAT)活性和丙二醛(MDA)含量降低,MDA含量在土壤盐度降低后第14天接近于低盐对照;土壤盐度降低后棉花叶片中可溶性糖、游离氨基酸和脯氨酸含量降低,且接近于低盐对照。上述结果表明土壤盐度降低后,棉花叶片生理功能逐渐恢复,进而实现棉花生长发育的恢复补偿。棉花叶片生理功能在土壤盐度降低后的恢复能力存在品种间差异,鲁棉研37号较苏棉22号叶片生理功能表现出更强的恢复能力。     

Adaptability to drought in sugar beet cultivars

The effects of NaCl and polyethylene glycol (PEG) on superoxide dismutase (SOD) and peroxidase (P) activities, lipid peroxidation (LP) and proline content in seeds and leaves of drought tolerant (FC-506 and MS-100) and drought sensitive (MS-612 and MS-13) sugar beet cultivars were examined. After PEG and NaCl treatment in tolerant cultivars both in seeds and leaves SOD activity mainly increased, though P activity increased only in leaves of tolerant cultivars. In drought sensitive cultivars the decrease of SOD and P activity was mostly observed. LP increased in seeds and leaves of all examined cultivars. The proline content increased in the leaves of examined cultivars and was significantly higher in drought tolerant plants. On the other hand, in the seeds only slight increase in proline content was found. The results obtained indicated that drought tolerance could be correlated with high proline content and enzymatic defense against lipid peroxidation.     

Effects of putrescine and ethephon on some oxidative stress enzyme activities and proline content in salt stressed spinach leaves

The effects of putrescine and ethephon on peroxidase (POD; EC 1.11.1.7), polyphenol oxidase (PPO; EC 1.14.18.1), catalase (CAT; EC 1.11.1.6) activities and proline content in spinach leaves under saline stress were investigated. In control conditions, putrescine increased PPO and CAT activities and proline content, but decreased POD activity. Ethephon increased these three enzyme activities but did not affect proline content. In saline conditions, putrescine increased POD and CAT activities and proline content, while it decreased PPO activity. Ethephon increased both PPO and CAT activities and proline content, but decreased POD activity. Putrescine and ethephon have opposite effects on the enzyme activities and proline accumulation because they acts as antagonists.     

Effect of Drought Stress on Certain Morphological and Physiological Characteristics of a Resistant and a Sensitive Canola Cultivar

Water stress is one of the main abiotic factors that reduces plant growth, mainly due to high evaporative demand and low water availability. In order to evaluate the effects of drought stress on certain morphological and physiological characteristics of two canola cultivars, we conducted a factorial experiment based on a completely randomized design. The findings show that drought stress exacerbations result in the plant's response to stress due to increased canola resistance caused by changes in plant pigments, proline, catalase, ascorbate peroxidase, peroxidase, superoxide dismutase and malondialdehyde, glucose, galactose, rhamnose and xylose. These in turn ultimately influence the morphological characteristics of canola. Drought stress reduces the concentration of carotenoids, chlorophyll a, chlorophyll b, total chlorophylls; however, glucose, galactose, rhamnose, xylose, proline, catalase, ascorbate peroxidase, peroxidase, superoxide dismutase, malondialdehyde (in leaves and roots) and the chlorophyll a and b ratios were increased. Reduction of plant height, stem height, root length, fresh and dry weight of canola treated with 300 g/l PEG compared to non‐treatment were 0.264, 0.236, 0.394, 0.183 and 0.395, respectively. From the two canola cultivars, the morphological characteristics of the NIMA increased compared to the Ks7 cultivar. Interaction effects of cultivar and drought stress showed that NIMA cultivar without treatment had the highest number of morphological characteristics such as carotenoid concentration, chlorophyll a, chlorophyll b, total chlorophylls a and b, whereas the cultivar with 300 g/l PEG (drought stress) had the highest amount of proline, malondialdehyde, soluble sugars and enzymes in leaves and roots. Increasing activity of oxidative enzymes and soluble sugars in canola under drought stress could be a sign of their relative tolerance to drought stress.     

Response of barley seedlings to water deficit and enhanced UV-B irradiation acting alone and in combination

Responses of barley seedlings to water deficit (WD) induced by polyethylene glycol (PEG 6000) and ultraviolet (UV-B; 280–320 nm) radiation and their interaction (UV-B + WD) were examined. A decrease in dry matter yield and water content of leaves and roots was observed following application of WD and UV-B + WD, while no changes were found after treating barley plants with UV-B. Proline content was increased in leaves under WD conditions and UV-B + WD. In contrast, UV-B treatment had no effect on the accumulation of proline in leaves of barley plants. Changes in root proline content showed a varied response: WD induced an increase in the level of this amino acid, while UV-B as well as UV-B + WD suppressed root proline content. The lipid peroxidation product malondialdehyde (MDA) was increased in leaves under WD and UV-B + WD stresses. Root MDA content increased in WD-stressed plants, but it decreased in the case of combined application of both stresses. The applied stress factors operated in a variable manner on phenylpropanoid metabolism. Phenylalanine ammonia-lyase (PAL) activity in leaves and roots was stimulated after exposure to WD and application of UV-B + WD stresses, while UV-B stress did not affect its activity. On the other hand, UV-B treatment enhanced the activity of 4:coumarate-CoA ligase (4CL) in leaves and this enhancement was positively correlated with the accumulation of anthocyanins and flavonols. However, the combined application of WD and UV-B reduced the positive effect of UV-B on the accumulation of these compounds and the activity of 4CL. Surprisingly, anthocyanins and flavonols were not detected in roots of examined barley seedlings despite increased 4CL activity. The results suggest that UV-B-induced activation of 4CL as well as accumulation of anthocyanin and flavonols in leaves is beneficial for the response to this stress factor. On the other hand, WD-induced reduction of the effect of UV-B on 4CL activity and the contents of anthocyanin and flavonol might be a cause of membrane damage in UV-B- and WD-stressed plants. In addition, conversely to what could be expected, the UV-B effect was perceived by the water-stressed roots, which exhibited reduced lipid peroxidation (MDA) and proline accumulation in WD-stressed plants exposed to UV-B.     

Peroxidase activities of two rice cultivars differing in salinity tolerance as affected by proline and NaCl

Proline content, ion accumulation, cell wall and soluble peroxidase activities were determined in control and salt-treated calli (150 nM NaCl) and whole plants (30 mM NaCl) of two rice cultivars (salt sensitive cv. IKP and salt tolerant cv. Aiwu). Under salinity, the highest accumulation of Na⁺, Cl^? and proline occurred in calli, roots and younger leaves of cv. IKP, coupled with the highest decrease in K⁺ content; accumulations of Na⁺ and Cl^? were restricted to older leaves in cv. Aiwu. Relative growth rates of calli and roots or shoots from both cultivars were not linked to peroxidase activities. High concentrations (1 M) of exogenously applied glycerol did not inhibitin vitro activities of soluble peroxidase extracted from control and salt-treated calli or plants. Conversely, 35–55% (in cv. IKP) or 60–80% (in cv. Aiwu) of soluble peroxidase activities were found in presence of isosmotic proline concentration. There were no differences between proline and glycerol effects onin vitro cell wall peroxidase activities.     

Proline controls the level of polyamines in common sage plants under normal conditions and at UV-B irradiation

Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4–5 true leaves were treated for 12, 24, 36, or 48 h with proline added to nutrient medium to a final concentration of 5 mM, or irradiated with UV-B light (12.3 kJ/m² for 10 min), or subjected to combined action of these factors. In these plants, activity of proline dehydrogenase (PDH), the content of proline, and the contents of free and conjugated polyamines were determined in the leaves and roots. It was shown that, in control plants, the content of endogenous proline was close to zero. In the presence of proline in medium, its total content in the roots was 9 μmol/g fr wt in 12 h of exposure, whereas in the leaves the content of proline increased only in 24 h and achieved only 1 μmol/g fr wt. The content of free putrescine increased in the leaves and especially in the roots after 10-min irradiation with UV-B light. The biosynthesis of putrescine was induced in the presence of proline in medium and was observed earlier than after UV-B irradiation. UV-B irradiation affected not only the synthesis of putrescine but also that of spermidine and spermine; it also induced accumulation of their soluble conjugates. Exogenous proline enhanced putrescine synthesis but inhibited the formation of polyamine soluble conjugates. At combined treatment of the two factors, the content of free putrescine in the leaves displayed a tendency to the rise and in the roots, to the decrease. At the same time, the content of polyamine free conjugates increased in both leaves and roots. All these facts could be considered as an indirect indication of relationship between proline and polyamine biosyntheses. We can also state that an artificially created high proline concentration in common sage tissues characterized of its low constitutive level resulted in disturbances in the homeostasis of low-molecular cell metabolites and induced a requirement in its restoration by diverse ways. This agrees with activation of PDH, a key enzyme of proline degradation. Induction of polyamine biosynthesis and changes in the content of their soluble conjugates might be one of the ways for such restoration. Under stress conditions, the high proline concentration is not toxic for plants because polyamines and proline are the components of the plant defense system, thus weakening damaging effects of abiotic stressors.     

Effects of exogenous abscisic acid on some physiological responses in a popular aromatic indica rice compared with those from two traditional non-aromatic indica rice cultivars

The poor productivity and local confinement of indigenous aromatic rice varieties are mostly due to their susceptibility to salinity/drought/abscisic acid (ABA)-mediated abiotic stresses. It is thus essential to study the effects of several stress factors on their physiological parameters so as to improve their tolerance mechanism and enhance their global demand. Previously, we studied the effect of salinity stress on the physiological and molecular responses of the common aromatic rice Gobindobhog. The objective of this study was to understand the influence of exogenous ABA on some biochemical parameters in Gobindobhog, and comparison with those from non-aromatic M-1-48 and Nonabokra rice. The highest endogenous hydrogen peroxide content and membrane lipid peroxidation (increased malondialdehyde and lipoxygenase activity) were found in ABA-treated Gobindobhog leaves. While the catalase activity was down regulated the most in ABA-treated Gobindobhog leaves, the guaiacol peroxidase activity was induced maximally, indicating the protective role of peroxidase rather than catalase, during ABA-induced oxidative damages. The antioxidant, anthocyanin, showed the highest level in ABA-treated Nonabokra. Enhanced cysteine, following ABA exposure and the highest levels of reducing sugars, total amino acids, proline, and polyamines (putrescine and spermidine) recorded in Gobindobhog, probably served to shield from ABA-induced stress injuries, whereas the spermine levels were comparable in ABA-treated Nonabokra and Gobindobhog. The aroma content, intensified after ABA treatment, was markedly noted in Gobindobhog. Thus, the systematic examination of ABA-mediated stress revealed the most prominent oxidative damages in Gobindobhog, even higher than M-1-48, with a concomitant enhancement in peroxidase system and particularly osmolyte or polyamine levels to ensure its sustenance.     

Bacterial endophytes contribute to abiotic stress adaptation in pepper plants (Capsicum annuum L.)

Endophytes are nonpathogenic plant-associated bacteria that can play an important role in plant vitality and may confer resistance to abiotic or biotic stress. The effects of 5 endophytic bacterial strains isolated from pepper plants showing 1-aminocyclopropane-1-carboxylate deaminase activity were studied in sweet pepper under in vitro conditions. Four of the strains tested showed production of indole acetic acid. Plant growth, osmotic potential, free proline content, and gene expression were monitored in leaves and roots under control and mild osmotic stress conditions. All indole acetate producers promoted growth in Capsicum annuum L. 'Ziegenhorn Bello', from which they were isolated. Osmotic stress caused an increase in the content of free proline in the leaves of both inoculated and noninoculated plants. Inoculated control plants also revealed higher proline levels in comparison with noninoculated control plants. Differential gene expression patterns of CaACCO, CaLTPI, CaSAR82A, and putative P5CR and P5CS genes during moderate stress were observed, depending on the bacterium applied. Inoculation with 2 bacterial strains, EZB4 and EZB8 (Arthrobacter sp. and Bacillus sp., respectively), resulted in a significantly reduced upregulation or even downregulation of the stress-inducible genes CaACCO and CaLTPI, as compared with the gene expression in noninoculated plants. This indicates that both strains reduced abiotic stress in pepper under the conditions tested.     

The effects of exogenous polyamines on some biochemical changes during drought stress in Ctenanthe setosa (Rosc.) Eichler

Morphological and biochemical changes in plant cells are known as important events for adaptation to stress. In this study, in Ctenanthe setosa leaves to which polyamines were applied during drought stress, changes in the activity of peroxidase, reducing sugar, proline and soluble protein levels were investigated. The three common polyamines, putrescine, spermidine and spermine were exogenously treated through the leaves. The polyamines were sprayed onto the leaves at 5 x 10(-5) M. In the leaves to which polyamines were applied the peroxidase activity decreased, soluble protein increased. Also, it was determined that putrescine and spermidine caused an increase in the amount of proline and in reducing sugar. However, increase was not observed in the leaves to which spermine was applied. In addition, we observed an increase in the activity of peroxidase, proline and reducing sugar levels, and a decrease in soluble protein level in the control ones and the leaves to which polyamines were applied during drought stress. As a result, the effect of polyamine on leaf rolling may be explained through the contribution to osmotic adjustment of the increase in proline, reducing sugar and soluble protein contents.     

Heavy Metals Induce Lipid Peroxidation and Affect Antioxidants in Wheat Leaves

The possible role of Zn and Cr as catalytic inducers of free radicals in wheat leaves was investigated. Treatment of excess heavy metals decreased the chlorophyll and carotenoid content in wheat leaves with the increase in time of excision. A sharp increase in proline accumulation was marked with the increase in metal concentration. Total peroxide content and lipid peroxidation measured as malondialdehyde content showed uniform increase under metal treatment in excised leaves. At almost all concentrations, catalase, guaiacol peroxidase and superoxide dismutase activities decreased with a minor increase in the earlier days of excision. Though glutathione content decreased ascorbate content showed significant increase in wheat leaves under heavy metal treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

24-epibrassinolide and/or putrescine trigger physiological and biochemical responses for the salt stress mitigation in Cucumis sativus L.

Brassinosteroids (BRs) and polyamines, well-established growth regulators, play a key role in abiotic stress response in plants. In the present study, we examined the role of 24-epibrassinolide (EBL, an active BR) and/or putrescine (Put) in the salt-induced stress in cucumber. The 15-d-old plants were exposed to 100 mM NaCl and they were subsequently treated by exogenous EBL and/or Put. The salt stress reduced significantly plant growth and gas-exchange parameters, and increased proline content and electrolyte leakage in the leaves. Toxic effects induced by salt stress were completely overcome by the combination of EBL and Put. EBL and/or Put treatments improved the growth parameters of the NaCl-treated plants, such as shoot length, root length, fresh and dry mass. Our data also indicated that applications of EBL and Put upregulated the activities of the antioxidant enzymes, such as catalase, peroxidase, and superoxide dismutase under salt stress.     

Effect of Light and Benzyladenine on Dark-Treated Growing Rice (Oryza sativa) Leaves II. Changes in Peroxidase Activity

Changes in peroxidase activity were studied in the attachedfirst leaf of dark-treated Oryza sativa L. cv. Bala seedlingsin response to benzyladenine and light treatments during laterperiods of leaf growth, prior to maturation. Darkness causeda mild decrease in peroxidase activity; but in illuminated leaves,the enzyme activity was stable at all times. There was a sharprise in peroxidase activity in dark-treated leaves upon lightor benzyladenine application, irrespective of the time of treatment.Benzyladenine treatment to illuminated leaves also caused arise in peroxidase activity. Exogenous hydrogen peroxide, glycolateand amizol resulted in a rise in peroxidase activity, whichwas further enhanced by benzyladenine treatment in both lightand dark incubated leaves. Proline maintained chlorophyll levels,whereas hydroxyproline caused chlorophyll degradation. Benzyladenineenhanced the proline effect and counteracted the hydroxyprolineeffect on chlorophyll. Both proline and hydroxyproline increasedperoxidase activity in the leaves of light and dark incubatedseedlings, and the enzyme activity further increased after benzyladeninetreatment. (Received December 7, 1984; Accepted May 8, 1985)     

Antioxidant defense system,lipid peroxidation,proline-metabolizing enzymes,and biochemical activities in two <Emphasis Type="Italic">Morus alba</Emphasis> genotypes subjected to NaCl stress

Salt stress-induced changes in antioxidant enzymes, lipid peroxidation, proline and glycine betaine contents, and proline-metabolizing enzymes were examined in the leaves of two mulberry cultivars (Local and Sujanpuri). With increasing salinity up to 150 mM NaCl, superoxide dismutase, catalase, ascor-bate peroxidase, guaiacol peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were increased in both cultivars as compared to control, but more pronounced increase was observed in cv. Local. Salt stress enhanced the rate of lipid peroxidation (as indicated by increasing MDA content) in both cultivars. Under NaCl stress, cv. Local showed less change in the MDA content than cv. Sujanpuri. Salt stress resulted in a significant accumulation of free proline in mulberry leaves, and more accumulation was detected in cv. Local than cv. Sujanpuri. The leaves of cv. Local showed 9-fold accumulation of glycine betaine in comparision with cv. Sujanpuri after 20 days at 150 mM NaCl. A decrease in proline oxidase activity and an increase in γ-glutamyl kinase activity were observed with increasing NaClconcentration. The relative water content and electrolyte leakage also decreased after increasing the NaCl concentration, but a decrease was more pronounced in cv. Sujanpuri than in cv. Local. The results indicate that oxidative stress may play an important role in salt-stressed mulberry plants and cv. Local have more efficient antioxidant characteristics, which could provide for a better protection against oxidative stress.     

Ameliorative Role of Pre-Sowing Proline Treatment in <i>Coriandrum sativum</i> L. Seedlings under Mercury Toxicity

Heavy metal toxicity is one of the major ecosystem concerns globally in present time and is also responsible for significant threat to agronomic crops. The current work was conducted to investigate the possible ameliorative role of proline in Coriandrum sativum L. seedlings treated with mercury (Hg). The seedlings were exposed to different concentrations of Hg (0, 0.1, 0.3 and 0.5 mM) for 20 days. The effects of pre-sowing treatment with proline were studied on C. sativum seedlings in terms of pigment (chlorophylls, carotenoids and anthocyanins), malondialdehyde (MDA), antioxidant compound (glutathione, total phenolic compounds, ascorbic acid) and osmolytes (proline, glycine betaine). Additionally, activities of antioxidant enzymes, namely catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) were also studied. A strong decline of photosynthetic pigment concentrations was observed in leaves of C. sativum under Hg toxicity. Treatment of seeds with proline reduced the loss of photosynthetic pigments, counteract Hg-triggered oxidative stress, likely preserving the functionality of antioxidant apparatus under Hg stress. The increment of total polyphenols and glycine betaine also contributed in ameliorating Hg toxicity, suggesting the use of exogenous proline as a potential method to enhance the plant tolerance against heavy metal stress.     

外源一氧化氮对氯化钠处理下秋茄幼苗抗氧化系统的调节效应

研究了外源一氧化氮(NO)供体硝普钠(SNP)对NaCl处理下红树植物秋茄(Kan-deliacandel)幼苗叶片中抗氧化酶活性、抗氧化物质及脯氨酸含量的影响。结果表明:NaCl处理下,秋茄幼苗叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)等4种活性氧清除酶的活性均受到明显抑制(P<0.05),SNP可以不同程度地恢复SOD、POD、CAT的活性,但对APX活性影响不大;SNP提高谷胱甘肽(GSH)及类胡萝卜素(Car)的含量,促进脯氨酸含量的上升,显著降低叶片中过氧化氢(H2O2)和丙二醛(MDA)的累积。表明外源NO可以缓解NaCl处理诱导的秋茄幼苗叶片氧化损伤,降低膜脂过氧化水平,有利于秋茄适应盐生环境。