NaCl Stress Conditions Research Articles

Characterization of type 3 metallothionein-like gene (OsMT-3a) from rice, revealed its ability to confer tolerance to salinity and heavy metal stresses

Salinity is significantly impeding agricultural productivity globally. As an ameliorative strategy, the quest for salinity tolerance genes and pathways to counter this problem is on the rise. In this study, we screened a cDNA library from rice (cultivar Egyptian Yasmine) grown under salinity stress, and isolated a metallothionein-like type 3 (OsMT-3a) gene. The function of the gene was characterized in Escherichia coli cells and its expression was analyzed in two rice cultivars having contrasting salinity tolerance. Overexpression of OsMT-3a in KNabc, salinity-sensitive E. coli mutant cells, showed improved salinity tolerance. The hydrogen peroxide (H2O2) concentration in OsMT-3a-transformed cells was less than one-third of that in control cells under salinity stress conditions. Under high concentrations of external H2O2, OsMT-3a-overexpressing E. coli cells showed enhanced growth, whereas the growth of control cells was completely retarded. Constitutive overexpression of OsMT-3a also showed enhanced E. coli tolerance against metal stress, particularly, for Cd2+ in comparison to control cells, in terms of growth performance. OsMT-3a expression was highly induced by NaCl treatment in the leaves of the salinity-tolerant cultivar Egyptian Yasmine; however, it was not induced in the salinity-sensitive cultivar Sakha 102. The expression of OsMT-3a was also up-regulated by Cd2+ and Cu2+ treatments in the shoots of Egyptian Yasmine with increased accumulation of the metal ions in comparison to Sakha 102. Egyptian Yasmine leaves had lower reactive oxygen species (ROS) (O2− and H2O2) concentrations than Sakha 102 under both NaCl and CdCl2 stress conditions. Collectively, these results suggest that the OsMT-3a gene confers tolerance not only to salinity but also to heavy metal stress, by detoxifying the ROS generated by these stresses. Thus, OsMT-3a would play a key role in salinity tolerance in rice via ROS scavenging.

Identification and validation of reference genes for quantitative real-time PCR under salt stress in a halophyte, Sesuvium portulacastrum

Sesuvium portulacastrum L. is a facultative halophyte with potential applications in phytoremediation and phytodesalination and offers as a system to understand mechanisms of salt adaptation. However, studies on gene identification, characterization and transcriptomics of this halophyte are limited due the paucity of genome sequence information and validation of gene expression data through quantitative real time-PCR (qRT-PCR). qRT-PCR is a reliable method for exact quantification of gene expression, but is dependent upon the selection of suitable reference gene(s). In the present study, using Sesuvium RNA-Seq data, we identified ten reference genes such as elongation factor 1-α, ubiquitin-conjugating enzyme E2, TATA-box binding protein, DnaJ-like protein, β-tubulin, glyceraldehyde 3-phosphate dehydrogenase, eukaryotic initiation factor 4a, RNA-dependent RNA polymerase 1, α-tubulin and pentatricopeptide repeat and validated their stable expression in root and shoot tissues under 0, 100 and 250mM NaCl stress conditions. Five different statistical methods viz. Delta Ct, NormFinder, BestKeeper, geNorm and ReFinder were used to establish the most suitable reference genes for root (UCE 2, TBP, EF1-α) and shoot (α-TUB, EIF4a, EF1-α). Additionally, the expression of five salt responsive genes was calculated under salt stress using the best reference genes and compared with RNA-Seq data. The comparison between real time and RNA-Seq data showed a high correlation (r2=0.875), supporting the selection of the suitable reference genes. This study provides a good starting platform for successful gene quantification in S. portualcastrum.

The ameliorative effects of 24-epibrassinolide on shoot organogenesis inhibition occurring under NaCl-stressed conditions in cultures of cotyledon and hypocotyl explants of tomato (Lycopersicon esculentum Mill.)

AbstractIn this study, possible effects of 24-epibrassinolide (24-epiBL) pretreatment against NaCl stress were investigated usingin vitroshoot organogenesis from cotyledon and hypocotyl explants in M-28 tomato hybrid cultivar. The cotyledon and hypocotyl explants of 10-day sterile seedlings were treated with 1 μM and 2 μM 24-epiBL solutions (prepared with 70% acetone) for 30 seconds and applied explants were cultured on MS medium supplemented with 2 mg/l 6-benzylaminopurine (BAP) + NaCl (0, 20, 40, 60, 80 and 100 mM). It was determined that the regeneration percentage as well as the shoot number/explant, the shoot length and the leaf number/shoot derived from both explants suffered NaCl stress after 30 days. 24-epiBL pretreatment against NaCl stress showed ameliorative effects and hypocotyl explants gave better results than cotyledon explants for these growth parameters. Different stages of shoot organogenesis from hypocotyl explants applied with 24-epiBL under salt stress were observed with scanning electron microscopy. As a result, it was shown that 24-epiBL treatment against NaCl stress may play an effective role in salt tolerance in M-28 tomato hybrid cultivar.

Cloning and molecular characterization of a ferulate-5-hydroxylase gene from water chestnuts (Trapa bicornis Osbeck.)

Ferulate 5-hydroxylase (F5H), a cytochrome P450 monooxygenase, has been indicated to function in the monolignol biosynthesis of sinapyl alcohol, namely the precursor of syringyl lignin during phenylpropanoid metabolism. In the present study, a full-length cDNA clone encoding F5H, designated as TbF5H1, was cloned from water chestnuts (Trapa bicornis Osbeck.) using RT-PCR and RACE. Sequence analysis of TbF5H1 protein revealed the presence of highly conserved motifs shard by P450 s, such as heme binding cysteine, oxygen binding I-helix, and E-R-R triade. Subsequently, TbF5H1 was expressed in bacterial system as a recombinant protein, which was used to ascertain kinetic parameters of the protein with the Km and Vmax values of 2.40 μM and 3.35 pkat mg−1, respectively. Together with high identity with other plant F5Hs based amino acid sequences, this result suggested that TbF5H1 had a biological function similar to its homologues in S lignin synthesis. Western blotting analysis using anti-TbF5H1 serum towards total proteins extracted from roots, stems, leaves, and flowers, detected a protein with a molecular weight of about 57 kDa. Quantitative real-time PCR analysis revealed the transcript level of TbF5H1 was higher in leaves than in other tested tissues. Interestingly, TbF5H1 was differentially expressed in response to various stresses, including salt (NaCl), hydrogen peroxide (H2O2) and heavy metal (lead), as well as elicitation by methyl ester jasmonate (MeJA). The expression of TbF5H1 was not significantly altered under NaCl or lead stress conditions, whereas a significant increase in TbF5H1 expression was detected after elicitation of H2O2 and MeJA, respectively. Moreover, there existed a fine coordination between expression of TbF5H1 and contents of certain nonenzymatic antioxidants. These results indicated that integrated with some redox components, TbF5H1 gene should contribute to the acclimation of T. bicornis to oxidative stress, which is modulated by MeJA.

Arginine decarboxylase ADC2 enhances salt tolerance through increasing ROS scavenging enzyme activity in Arabidopsis thaliana

Soil salinity, one of the major abiotic stresses limiting plant growth and productivity, affects large terrestrial areas of the world. Putrescine (Put), one of major Polyamines (PAs) widely present in organisms, is a type of low-molecular-weight aliphatic nitrogenous bases with function of regulating cell activities. Arginine decarboxylase (ADC) is a key rate-limiting enzyme in Put synthesis. It has been reported that loss-of-function mutant of the encoding gene AtADC2 is intolerant to salt stress in Arabidopsis. However, the effect of overexpression of AtADC2 on plant salt tolerance and the mechanisms about how ADC is involved in the response of plants to salt stress remain unknown. In this study, both overexpression lines of AtADC2 (AtADC2-OE), which has higher endogenous Put concentration, and loss-of-function mutant (adc2-3) were treated by salt stress. Under 150 mM NaCl stress condition, the growth of the mutant adc2-3 was more strongly inhibited than the wild type (Col-0). However, AtADC2-OE was less affected and displayed an enhanced salt tolerance. The chlorophyll content was detected to be significantly enhanced in AtADC2-OE lines and reduced in adc2-3 compared with in Col-0. These results indicated AtADC2-OE lines had more tolerance to salt stress. In addition, AtADC2 expression is up-regulated by salt stress in primary root tip of Arabidopsis seedling. Under salt stress, the contents of malonaldehyde, superoxide (O2.−) and hydrogen peroxide (H2O2), were increased in adc2-3, while H2O2 content was somewhat decreased in AtADC2-OE lines, as compared with those in Col-0. Determination of enzyme activities showed that after salt treatment, the activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced significantly in AtADC2-OE lines, but varied inconspicuously in adc2-3. Taken together, our results reveal that, under salt stress, the increase in both expression of AtADC2 gene and Put accumulation regulates the activities of SOD and CAT to enhance the salt resistance of Arabidopsis thaliana.

Putative 3-nitrotyrosine detoxifying genes identified in the yeast Debaryomyces hansenii : In silico search of regulatory sequences responsive to salt and nitrogen stress

Background: During saline stress, the yeast Debaryomyces hansenii has as a strategy to avoid the oxidation of proteins the synthesis of tyrosine, which reacts with nitrogen radicals to form 3-nitrotyrosine, these contributes to the high halotolerace of the yeast, because it prevents the effects of associated oxidative stress. However, it has not been determined how does D. hansenii counteract the presence of this toxic compound. In this work we evaluated the D. hansenii capacity to assimilate 3-nitrotyrosine as a unique nitrogen source, and measured its denitrase activity under NaCl stress. In order to identify putative genes related to the assimilation of 3-nitrotyrosine, we performed an in silico search in the promoter regions of D. hansenii genome. Results: We identified 15 genes whose promoter had binding sequences for transcriptional factors of sodium, nitrogen and oxidative stress with oxidoreductase and monooxygenase GO annotations. Two of these genes, DEHA2E24178g and DEHA2C00286g coding for putative denitrases and having GATA sequences, evaluated by RT-PCR, showed a high expression in sodium and nitrogen stress. Conclusions: D. hansenii can grow in presence of 3-nitrotyrosine as the only nitrogen source, and have a high especific denitrase activity to degradate 3-nitrotyrosine in 1 and 2 M NaCl stress conditions. The results suggest that given the lack of information for transcriptional factors in D. hansenii , genes identified by our in silico analysis may help to explain 3-nitrotyrosine assimilation mechanisms. Normal 0 false false false ES-MX X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif; border:none; mso-ansi-language:ES-MX; mso-fareast-language:ES-MX;}

Exogenous proline enhances nutrient uptake and confers tolerance to salt stress in maize (Zea mays L.)

Proline accumulation is the main adaptive mechanism to salinity in plants. The pot experiments were carried out to mitigate the adverse effects of NaCl stress on BARI Hybrid Maize-5 and Hybrid Maize Pacific-987 by exogenous application of proline. Plants were exposed to different concentrations of NaCl at vegetative stage. Proline solutions were sprayed over maize leaves at both vegetative and tasseling stages. NaCl stress caused significant reductions in plant growth of maize. NaCl stress at 50 mM drastically reduced the growth of maize plant. Salt stress also reduced reproductive growth, grain yield, chlorophyll contents, K+/Na+ ratio and nutrient (NPS) uptake in both maize varieties. Exogenously applied proline improved growth and grain yield of BARI Hybrid Maize-5 at 25 mM NaCl stress condition. Additionally, BARI Hybrid Maize-5 conferred tolerance to 50 mM NaCl stress with 25 mM proline. Proline application significantly increased K+/Na+ ratio and nutrient uptake by maize under salt stress. The present study suggests that proline improves salt tolerance of maize by increasing the K+/Na+ ratio and nutrient uptake, particularly P uptake.Progressive Agriculture 27 (4): 409-417, 2016

Analysis of fatty acid composition of PGPR Klebsiella sp. SBP-8 and its role in ameliorating salt stress in wheat

A halotolerant plant-growth-promoting rhizobacteria (PGPR) can ameliorate salt stress in associated plants by various mechanisms. Therefore, the present study aimed to characterize a PGPR Klebsiella sp. SBP-8 for its ability to tolerate salt stress and to study the mechanism of PGPR-mediated mitigation of salt stress in the wheat plant. The abiotic stressors result in multiple changes in the fatty acid composition of Klebsiella sp. SBP-8, helping the membrane to keep its integrity, fluidity, and function for its growth under salt (NaCl) stress conditions. The changes in fatty acid composition of test organism were analyzed by fatty acid methyl ester (FAME) analysis under varying saline conditions. The spectroscopy (GC-MS) profile of cell extract at different salt concentrations was comprised of hydrocarbons, and fatty alcohols with varying carbon chain length. Inoculation of Klebsiella sp. SBP-8 to wheat seedling showed increase in proline, total soluble sugar, and total protein content of treated plants. Bacterial inoculation also decreased the concentration of salinity-induced malondialdehyde (MDA) content. In addition, bacterial inoculation also increased the various antioxidative enzymes like superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) in treated plants. It is likely that bacterial inoculation alleviated the salt stress to wheat plant by co-ordination of antioxidative machinery, and improvement in osmolyte contents. Therefore, the present study suggests that bacterial-inoculated wheat plants were able to cope better with salt stress than uninoculated control, therefore it can serve as a promising bio-inoculant for enhancing the growth of wheat like cereal crops under saline stress.

Overexpression of a cytosolic ascorbate peroxidase from Panax ginseng enhanced salt tolerance in Arabidopsis thaliana

Ascorbate peroxidase (APX) plays an essential role in the antioxidant defense mechanism in the plant, serving in the ascorbate–glutathione cycle for the cellular H2O2 metabolism process. As the perennial plant, Panax ginseng Meyer encounters a lot of unfavorable growth conditions, and among them soil salinity significantly decreases the yield. Two APX genes from Panax ginseng were isolated and designated as PgAPX1 and PgAPX2, which are most similar with previously characterized cytosolic APX of Daucus carota and Spuriopimpinella brachycarpa, as revealed by sequence analysis of their deduced amino acid sequences. PgAPXs transcripts are most abundant in leaf tissue, whereas PgAPX1 expression level was higher compared to PgAPX2. Consistent with higher PgAPX1 expression during salt stress in ginseng, PgAPX1-overexpressing Arabidopsis lines (PgAPX1ox) increased the germination rate and root length compared with wild-type (WT) under 200 mM NaCl stress treatment. Furthermore, higher chlorophyll content, relative water content, total APX activity, proline content, and lower H2O2 accumulation were shown in PgAPX1ox plants compared to WT under 200 mM NaCl stress condition. Transcription analysis showed that PgAPX1oxArabidopsis lines were more salt-tolerant by upregulating the ion homeostasis mechanism.

Accumulation of antioxidants in rice callus (Oryza sativa L.) induced by β-glucan and salt stress

Salinity stress causes a considerable reduction in callus growth. Mushroom polysaccharides (beta-glucan) are the most promising groups of antioxidant compounds. An in vitro experiment was conducted to evaluate the potential function of exogenously applied beta-glucan in alleviating the accumulation of antioxidants in rice callus. In this study, morphological, chemical, and biochemical parameters of an embryogenic callus of the rice variety, MR269, were investigated under 200mM NaCl stress conditions after pre-treatment with (0, 0.5, 1 and 1.5 mg/L) beta-glucan in culture media. The present study sought to evaluate chemical, biochemical, and callus growth characterization. The results revealed that callus exposed to stressful media exhibited a significant decrease in callus growth and contents of K+ and Ca+2. In addition, significant accumulation of Na+ and Na+/K+ was found, as well as an enhanced enzymatic antioxidant system and elevated proline activities under NaCl conditions. Furthermore, exogenous addition of beta-glucan at 0.5-1.5mg/L under NaCl stress induced a pronounced, significant increase of callus growth, K+ and Ca+2 contents, and enzymatic antioxidant and proline activities. In contrast, a significant decrease was found in the levels of Na+ and Na+/K+, particularly in callus treated with NaCl. beta-Glucan ameliorates the adverse effects of NaCl stress, and the extent of amelioration depends on the type of beta-glucan agent as well as treatment duration (three months). The changes mentioned are important for determining the morphological, chemical, and biochemical parameters of salinity tolerance in callus. This study demonstrated that exogenous beta-glucan exhibits alleviation of the harmful effects of salt stress and increases salinity resistance in callus rice.

PENENTUAN KONSENTRASI KEMATIAN KALUS TEBU (Saccharum officinarum) VARIETAS BL DAN PS-862 PADA SELEKSI In Vitro UNTUK KETAHANAN TERHADAP SALINITAS

<p>ABSTRACT</p><p>Salinity (salt stress) is one of the different causes of decline in crop yields and productivity of sugarcane. One strategy for optimizing the production of sugarcane on saline land required tolerant varieties of salinity. This research was conducted to determine NaCl concentration that caused more than > 90% callus death on sugarcane (S officinarum) tissue culture and to investigate the protein profile of sugarcane callus BL and PS-862 varieties on saline (NaCl) stress condition. Sugarcane BL and PS-862 varieties were obtained from tissue culture. and those callus were sub-cultured in salinity media with composition of MS (Murashige-Skoog) as base medium and NaCl in various concentration (0%; 0.25%; 0.5%; 0.75%; and 1%). The results showed condition of NaCl addition on media by 1% concentration cause alteration on morphology of callus that 75% part of whole tissues become dark brown coloured that indicating the tissues death. At four weeks after sub-culture, the calli on both varieties obtain score 4. Lethal percentage of both varieties BL and PS-862 in 1% NaCl was 91,67%. This result were supported by protein profile analysis. that a thinner protein band in 1% NaCl treatment compared with control. This is indicating that in salinity stress causing the decrement of protein expression.</p><p> </p>

Effects of silicon on the growth of maize seedlings under normal, aluminum, and salinity stress conditions

ABSTRACTThe effects of silicon on seed germination and growth parameters of maize seedlings under normal, aluminum (Al), and sodium chloride (NaCl) stress conditions were investigated. The results indicated a dose-dependent relationship between silicon and growth parameters, except for germination attributes.Application of silicon (2 mM) accelerated amylase activity, decreased abscisic acid content, and increased indoleacetic acid and gibberellic acid contents of seedling, The results suggest that the beneficial effects of silicon, at least in part, are mediated by the balance of phytohormones. Exposure to Al (10 mM) significantly decreased all growth parameters of maize seedlings. Application of 2 mM silicon, however, alleviated Al stress and restored almost all growth attributes. Decrease of Al absorption, increase of fructan content, and improvement of amylase activity were considered as the mechanisms of ameliorative function of silicon in Al-stressed maize seedlings. Exposure to silicon, however, did not show beneficial effects on growth parameters of maize seedlings under salt stress conditions.

The effects of CaCl2 on fruit yield, quality and nutrient contents of tomato under NaCl stress conditions

In this study, the effects of CaCl2 on fruit yield, quality Ca/Na and K/Na ratios and Na content of tomato leaves under NaCl stress conditions were determined. The doses of 0, 6.8 and 16.8 mM CaCl2 were combined with the doses of 0, 44.4, 70.4 mM NaCl in complete nutrient solution. General, NaCl and CaCl2 decreased fruit yield, NaCl decreased stem amount, whereas it increased at 6.8 mM CaCl2. CaCl2 decreased fruit yield without NaCl, but it increased fruit yield significantly at 44.4 mM dose and caused tolerance to NaCl. The 6.8 mM dose of CaCl2 increased stem amount without NaCl. However, CaCl2 did not cause tolerance at high doses of NaCl in terms of growth. CaCl2 decreased brix of fruit, while NaCl increased it. CaCl2 increased brix without NaCl, but decreased it at 44.4 and 70.4 mM NaCl. CaCl2 and NaCl decreased fruit juice pH significantly. Besides, CaCl2 decreased fruit juice pH at 0 and 44.4 mM of NaCl. The number of fruits which were found to have blossom-end rot (NFBER) did not change without NaCl with the influence of CaCl2. However, CaCl2 applied at high doses of NaCl decreased the NFBER and provided tolerance to NaCl. Increasing dose of NaCl increased significantly the Na content in leaves, but the addition CaCl2 decreased significantly the Na content in leaves. Increasing the dose of CaCl2 applications at 0 and 44.4 mM NaCl levels increased the Ca/Na ratio in tomato leaves. But, the effect of CaCl2 on Ca/Na ratio of leaves was statistically insignificant. The addition of NaCl into the solution nutrient decreased the Ca/Na and K/Na ratios in tomato leaves. The effect of CaCl2 on the K/Na ratio of leaves was not found significant.

A betaine aldehyde dehydrogenase gene in quinoa (Chenopodium quinoa): structure, phylogeny, and expression pattern

Betaine aldehyde dehydrogenase (BADH) is widely considered as a key enzyme in glycine betaine metabolism in higher plants. Several paralogous genes encoding different isozymes of BADH have been identified and characterized in some plants; however, until now, only limited information is available about BADH genes in quinoa (Chenopodium quinoa). Here, we report the molecular cloning, structural organization, phylogenetic evolution, and expression profile of a BADH gene (CqBADH1) from quinoa. The translated putative CqBADH1 protein included five conserved features of the ALDH Family 10. Comparisons between the cDNA and genomic sequences revealed that the CqBADH1 gene contained 15 exons and 14 introns. Comparative screening of introns in homologous genes demonstrated that the number and position of the BADH introns were highly conserved among the BADH genes in Amaranthaceae plants and in other more distantly related plant species. A phylogenetic analysis showed that CqBADH1 had the closest relationship with a protein from Atriplex canescens and belonged to the ALDH10 family. Expression profile analyses indicated that CqBADH1 was expressed only in root, and showed time-dependent expression profiles under NaCl-stress condition. Moreover, in quinoa, NaCl stress led to increased levels of CqBADH1 mRNA accompanied by the accumulation of glycine betaine. This is the first study to describe a BADH gene in quinoa.

The effect on photosynthesis and osmotic regulation in Beta vulgaris L. var. Flavescens DC. by salt stress

This study was to investigate the effect of salt stress on physiological characteristics such as plant growth, photosynthesis, solutes related to osmoregulation of Beta vulgaris. A significant increase of dry weight was observed in 50 mM and 100 mM NaCl. The contents of Chl a, b and carotenoid were lower in NaCl treatments than the control. On 14 day after NaCl treatment, photosynthetic rate (PN), the transpiration rate (E) and stomatal conductance of CO2 (gs) were reduced by NaCl treatment. On 28 day after NaCl treatment, the significant reduction in g s and E was shown in NaCl 200 mM. However, PN and water use efficiency (WUE) in all NaCl treatments showed higher value than that of control. Total ion contents (TIC) and osmolality were higher than the control. On 14 day after treatment, the contents of proline (Pro) increased signifi cantly in 200 mM and 300 mM NaCl concentration compared with control, whereas on 28 day in all treatments it was lower than that of the control. The contents of glycine betaine (GB) increased with the increase of NaCl concentration. The contents of Na + , Cl , GB, osmolality and TIC increased with the increase of NaCl concentrations. These results suggested that under severe NaCl stress conditions, NaCl treatment did not induce photochemical inhibition on fluorescence in the leaves of B. vulgaris, but the reduction of chlorophyll contents was related in a decrease in leaf production. Furthermore, increased GB as well as Na + and Cl contents resulted in a increase of osmolality, which can help to overcome NaCl stress.

Nitric oxide and iron modulate heme oxygenase activity as a long distance signaling response to salt stress in sunflower seedling cotyledons

Nitric oxide is a significant component of iron signaling in plants. Heme is one of the iron sensors in plants. Free heme is highly toxic and can cause cell damage as it catalyzes the formation of reactive oxygen species (ROS). Its catabolism is carried out by heme oxygenase (HOs; EC 1.14.99.3) which uses heme both as a prosthetic group and as a substrate. Two significant events, which accompany adaptation to salt stress in sunflower seedlings, are accumulation of ROS and enhanced production of nitric oxide (NO) in roots and cotyledons. Present investigations on the immunolocalization of heme oxygenase distribution in sunflower seedling cotyledons by confocal laser scanning microscopic (CLSM) imaging provide new information on the differential spatial distribution of the inducible form of HO (HO-1) as a long distance in response to NaCl stress. The enzyme is abundantly distributed in the specialized cells around the secretory canals (SCs) in seedling cotyledons. Abundance of tyrosine nitrated proteins has also been observed in the specialized cells around the secretory canals in cotyledons derived from salt stressed seedlings. The spatial distribution of tyrosine nitrated proteins and HO-1 expression further correlates with the abundance of mitochondria in these cells. Present findings, thus, highlight a link among distribution of HO-1 expression, abundance of tyrosine nitrated proteins and mitochondria in specialized cells around the secretory canal as a long distance mechanism of salt stress tolerance in sunflower seedlings. Enhanced spatial distribution of HO-1 in response to NaCl stress in seedling cotyledons is in congruence with the observed increase in specific activity of HO-1 in NaCl stressed conditions. The enzyme activity is further enhanced by hemin (HO-1 inducer) both in the absence or presence of NaCl stress and inhibited by zinc protoporphyrin. Western blot analysis of cotyledon homogenates using anti-HO-1 polyclonal antibody shows one major band (29 kDa) of HO-1. NaCl-modulated HO-1 activity correlates with endogenous NO content in the cotyledons. Increased NO accumulation by hemin treatment also correlates with enhanced activity of HO-1 in both control and NaCl stress conditions. Present work indicates that NO positively modulates HO-1 activity in sunflower seedling cotyledons. NaCl stress tends to antagonize NO action on HO-1 activity. NO (from sodium nitroprusside; SNP) is probably positively modulating HO-1 activity by way of its interaction/binding with heme group. Present work also shows enhanced NO accumulation in seedling cotyledons both in the absence or presence of iron in the growth medium, in response to NaCl stress. Thus, a probable link between endogenous NO, NaCl stress and iron-homeostasis by way of modulation of HO-1 activity at early stage of sunflower seedling growth has been proposed.

Effects of Salt Stress on Ion Balance at Vegetative Stage in Rice (<i>Oryza sativa</i> L.)

Rice (Oryza sativa L.) plants were subjected to NaCl stress within 35 days. The shoot dry weight, root dry weight, total survival percentage and contents of inorganic ions in dry samples of stressed plants were measured to identify the physiological adaptive mechanisms by which rice plants at vegetative stage tolerate salt stresses. Laboratory testing of the 10 rice cultivars showed that the salt concentration for the treatment is especially significant for assessment of the relationship between ion accumulation and salt tolerance. Salt treatment strongly stimulated accumulations of Na+, Na+/K+ ratio, Cl- in shoot and root and reduced K+, NO3- contents in both organs under 1.2% NaCl stress condition, but not always under 0.6% NaCl concentration. It was shown significantly negative correlation (p<0.5) between the Na+ content and dry weight of shoot and root under 1.2% NaCl stress condition. Also, was founded significantly negative impact (p<0.5) of Cl- ions on biomass growth and survival rice plants and positive relationship (p<0.5) among the root dry weight and K+, NO3- content under the high NaCl concentration (1.2% NaCl). So, in addition to Na+, the contributions of Cl- to abiotic stresses of rice should not be ignored.

Effect of exogenous sucrose on growth and active ingredient content of licorice seedlings under salt stress conditions

Licorice seedlings were taken as experimental materials, an experiment was conducted to study the effects of exogenous sucrose on growth and active ingredient content of licorice seedlings under NaCl stress conditions. The results of this study showed that under salt stress conditions, after adding a certain concentration of exogenous sucrose, the licorice seedlings day of relative growth rate was increasing, and this stress can be a significant weakening effect, indicating that exogenous sucrose salt stress-relieving effect. The total flavonoids and phenylalanine ammonia lyase (PAL) activity were significantly increased, the exogenous sucrose can mitigated the seedling roots under salt stress, the licorice flavonoid content in the enhanced growth was largely due to the activity of PAL an increased, when the concentration of exogenous sucrose wae 10 mmol x L(-1), PAL activity reaching a maximum, when the concentration of exogenous sucrose was 15 mmol x L(-1), PAL activity turned into a downward trend, the results indicating that this mitigation has concentration effect. After applying different concentrations of exogenous sugar, the contents of liquiritin changes with the change of flavonoids content was similar. After applying different concentrations of exogenous sucrose, the content of licorice acid under salt stress was higher than the levels were not reached during salt stress, the impact of exogenous sucrose concentration gradient of licorice acid accumulation was not obvious.

Modulation of superoxide dismutase (SOD) isozymes by organ development and high long-term salinity in the halophyte Cakile maritima.

Superoxide dismutase (SOD) activity catalyzes the disproportionation of superoxide radicals into hydrogen peroxide and oxygen. This enzyme is considered to be a first line of defense for controlling the production of reactive oxygen species (ROS). In this study, the number and type of SOD isozymes were identified in the principal organs (roots, stems, leaves, flowers, and seeds) of Cakile maritima. We also analyzed the way in which the activity of these SOD isozymes is modulated during development and under high long-term salinity (400 mM NaCl) stress conditions. The data indicate that this plant contains a total of ten SOD isozymes: two Mn-SODs, one Fe-SOD, and seven CuZn-SODs, with the Fe-SOD being the most prominent isozyme in the different organs analyzed. Moreover, the modulation of SOD isozymes, particularly CuZn-SODs, was only detected during development and under severe salinity stress conditions. These data suggest that, in C. maritima, the occurrence of these CuZn-SODs in roots and leaves plays an adaptive role since this CuZn-SOD isozyme might replace the diminished Fe-SOD activity under salinity stress to overcome this adverse environmental condition.

Putative bacterial volatile-mediated growth in soybean (Glycine max L. Merrill) and expression of induced proteins under salt stress.

Plant root-associated rhizobacteria elicit plant immunity referred to as induced systemic tolerance (IST) against multiple abiotic stresses. Among multibacterial determinants involved in IST, the induction of IST and promotion of growth by putative bacterial volatile compounds (VOCs) is reported in the present study. To characterize plant proteins induced by putative bacterial VOCs, proteomic analysis was performed by MALDI-MS/MS after exposure of soybean seedlings to a new strain of plant growth promoting rhizobacteria (PGPR) Pseudomonas simiae strain AU. Furthermore, expression analysis by Western blotting confirmed that the vegetative storage protein (VSP), gamma-glutamyl hydrolase (GGH) and RuBisCo large chain proteins were significantly up-regulated by the exposure to AU strain and played a major role in IST. VSP has preponderant roles in N accumulation and mobilization, acid phosphatase activity and Na(+) homeostasis to sustain plant growth under stress condition. More interestingly, plant exposure to the bacterial strain significantly reduced Na(+) and enhanced K(+) and P content in root of soybean seedlings under salt stress. In addition, high accumulation of proline and chlorophyll content also provided evidence of protection against osmotic stress during the elicitation of IST by bacterial exposure. The present study reported for the first time that Ps. simiae produces a putative volatile blend that can enhance soybean seedling growth and elicit IST against 100 mmol l(-1) NaCl stress condition. The identification of such differentially expressed proteins provide new targets for future studies that will allow assessment of their physiological roles and significance in the response of glycophytes to stresses. Further work should uncover more about the chemical side of VOC compounds and a detailed study about their molecular mechanism responsible for plant growth.