NaCl Conditions Research Articles

Oxidfluoridsulfide der Lanthanoide vom Formeltyp M3OF5S (M = Nd, Sm, Gd–Ho) / Oxide Fluoride Sulfides of the Lanthanoids with the Formula M3OF5S (M = Nd, Sm, Gd–Ho)

First attempts to synthesize a lanthanoid(III) oxide fluoride sulfide were successful by reacting DyF3 and Dy2O3 with dysprosium and sulfur in a 2 : 5 : 1 : 3 molar ratio at 850 ◦C in tightly sealed tantalum ampoules. In analogy to the dysprosium compound Dy3OF5S, the other representatives of the M3OF5S series with M = Nd, Sm, Gd-Ho could be prepared as well. Almost phase-pure samples were obtained under similar flux-assisted (NaCl) conditions according to 2M +5MF3 +M2O3 + 3S →3M3OF5S. In the hexagonal crystal structure (space group: P63/m; a ≈ 961 - 939 pm, c ≈ 378 - 367 pm; c/a≈0.39,Vm ≈91 - 84 cm3 mol−1, Z = 2), the M3+ cations reside in ninefold anionic coordination realized as tricapped trigonal prisms formed by seven light (O2−/F−) and two heavier S2− anions. One light-anion position exhibits the exclusive character of F− in trigonal non-planar coordination (CN = 3), while the other position with a tetrahedral cationic environment (CN = 4) is mixed occupied by F− and O2− in a 2 : 1 ratio. The S2− anions are coordinated in a trigonal prismatic way by six M3+ cations. From the data of single-crystal X-ray structure analyses, no indication of any ordering for the O2− and F− anions could be obtained, but bond-valence and MAPLE calculations confirmed the results of electron-beam microanalyses carried out earlier to reveal ordered models for Dy3OF5S.

Comparaison des transports d'ions dans les feuilles du blé dur et du triticale cultivés en présence de sel: sélectivité K/Na et coût énergétique

The study of NaCl effects on wheat and triticale showed an increase in root biomass from the lowest dose (50 mM) in the two cereals and maintenance of shoot growth even at the highest concentration (200 mM). However, triticale shoot growth was decreased by 25% at 200 mM NaCl. Wheat absorbed and exported more Na+ ions to its shoots than triticale. The latter accumulated the majority of the absorbed sodium within its roots. In addition, triticale seems to be more selective towards K+ ions since it limited Na+ uptake and transport to shoots and ensured better K+ nutrition. The measurements of root respiration intensity in seedlings grown under saline (100 mM NaCl) and non saline (0 mM NaCl) conditions showed that in salt—treated wheat plants, respiration displayed no change, whereas in those of triticale, it was enhanced by 27% as compared to the control. This stimulation could be related to K/Na selectivity.

Electrochemical Method to Evaluate Rapid Degradation of Multi-Layer Coatings on High Strength Galvanized

Throughout history attempts have been made to protect galvanized steel using resin-based paints. Actually polyurethane compounds and polysiloxanes have been applied quite successfully to solve the problem of incompatibility with systems of galvanized coating systems generating highly resistive barriers to the passage of aggressive agents to and from the metal-polymer interface. The polymeric systems studied here provide excellent corrosion protection under conditions of extreme aggressiveness, such as NaCl and damage condition. Electrochemical techniques for the quality evaluation of coating performance were used, in particular the rapid electrochemical test applied on paints (REAP). The REAP test is an effective method to assess industrial coating systems usually having excellent corrosion resistance in NaCl solutions and good compatibility with galvanized steel. Also it is proposed the determination of a degradation index throughout the linear polarization resistance method LPR produced by the REAP test on multi-layer coatings.

Physiological Role of Sodium in the Growth of the Halophyte Suaeda salsa (L.) Pall. under High‐Sodium Conditions

It is well known that growth of Suaeda salsa (L.) Pall. is stimulated by NaCl application. However, the physiological role of sodium in the growth of Suaeda salsa has not been elucidated. We thus examined the physiological role of sodium in the growth of Suaeda salsa grown in nutrient solutions containing 5 mmol L−1 Cl− and graded concentrations of Na2SO4 Sodium concentrations in plant tissues increased as the growth medium salinity increased. The osmolality gradient between plant tissues and growth medium was maintained at constant levels despite the increase of osmolality in the growth medium. As a result, the amount of water absorbed by the plant tissues was not significantly affected by the salinity of the medium. The dry weight of the S. salsa plants did not increase significantly as sodium concentrations in plant tissues rose. As salinity of the medium increased, the contribution of water‐soluble sodium to the osmolality in the leaves, stems, and roots also rose. There was a significant positive correlation between sodium concentration and osmolality in plant tissues. These results suggest that sodium is the major cation contributing to the maintenance of high osmolality in plant tissues of S. salsa grown under the high‐salinity conditions. Therefore, under high‐salinity conditions, the physiological role of sodium may be to maintain water absorption by maintaining osmolality in the plant tissues, which would help explain the normal growth of S. salsa under high NaCl conditions.

High-efficiency transformation and selective tolerance against biotic and abiotic stress in mulberry, Morus indica cv. K2, by constitutive and inducible expression of tobacco osmotin

Osmotin and osmotin-like proteins are stress proteins belonging to the plant PR-5 group of proteins induced in several plant species in response to various types of biotic and abiotic stresses. We report here the overexpression of tobacco osmotin in transgenic mulberry plants under the control of a constitutive promoter (CaMV 35S) as well as a stress-inducible rd29A promoter. Southern analysis of the transgenic plants revealed the stable integration of the introduced genes in the transformants. Real-time PCR analysis provided evidence for the expression of osmotin in the transgenic plants under both the constitutive and stress-inducible promoters. Transgenic plants with the stress-inducible promoter were observed to better tolerate salt and drought stress than those with the constitutive promoter. Transgenic plants when subjected to simulated salinity and drought stress conditions showed better cellular membrane stability (CMS) and photosynthetic yield than non-transgenic plants under conditions of both salinity and drought stress. Proline levels were very high in transgenic plants with the constitutive promoter relative to those with the stress-inducible promoter. Fungal challenge undertaken with three fungal species known to cause serious losses to mulberry cultivation, namely, Fusarium pallidoroseum, Colletotrichum gloeosporioides and Colletotrichum dematium, revealed that transgenic plants with osmotin under control of the constitutive promoter had a better resistance than those with osmotin under the control of the stress-inducible promoter. Evaluation in next generation was undertaken by studying bud break in transgenic and non-transgenic plants under simulated drought (2% polyethylene glycol) and salt stress (200mM NaCl) conditions. The axillary buds of the selected transgenic lines had a better bud break percentage under stressed conditions than buds from non-transgenic mulberry lines. A biotic assay with Bombyx mori indicated that osmotin protein had no undesirable effect on silkworm rearing and feeding. We therefore conclude that 35S transgenic plants are better suited for both abiotic stress also biotic challenges (fungal), while the rd29A transgenic plants are more responsive to drought.

Oil and Protein Accumulation in Soybean Grains under Salinity Stress

Two factorial experiments based on randomized complete block design (RCBD) with three replications were conducted in 2007 and 2008, to evaluate grain development (four harvests) and rate and duration of oil and protein accumulation in three soybean cultivars (‘Williams’, ‘Zan’ and ‘L17’) under a non-saline (control) and three saline (3, 6 and 9 ds/m NaCl) conditions. Six seeds were sown in each pot filled with 900 g perlite, using 144 pots for each experiment. After emergence, seedlings were thinned and 4 plants were kept in each pot. Rate of oil accumulation up to maturity was not significantly affected by salinity. With increasing salinity, rate and percentage of protein accumulation, duration of oil and protein accumulation and oil and protein content per grain decreased, but oil percentage increased. Oil and protein yields per plant decreased as salinity increased. These reductions were mainly attributed to the short duration of protein and oil accumulation and grain yield per plant under saline conditions. ‘Williams’ had the highest rate and duration of protein accumulation and rate of oil accumulation, but ‘L17’ had the highest grain yield per plant. Consequently, differences in protein and oil yields per plant between these two cultivars were not statistically significant. However, ‘Zan’ had the lowest protein and oil yields, due to the lowest grain yield per plant.

Responses of physiological parameters, grain yield, and grain quality to foliar application of potassium nitrate in two contrasting winter wheat cultivars under salinity stress

AbstractAn experiment was conducted to test whether foliar application of KNO3 on wheat in the heading stage could reduce salinity‐induced injuries, produce high grain yield, and improve grain quality. Salt‐resistant DK961 and salt‐sensitive JN17 wheat cultivars under 0 or 100 mM–NaCl conditions were foliarly watered with distilled water or a 10 mM–KNO3 solution. The four treatments included: T1 (CK1), 0 mM NaCl + distilled water; T2, 0 mM NaCl + 10 mM KNO3; T3 (CK2), 100 mM NaCl + distilled water; T4, 100 mM NaCl + 10 mM KNO3. The results indicate that there were no differences (p > 0.05) in plant growth, grain yield, and grain quality between T2 and T1 in both cultivars, but these response variables were significantly lower in T3 than in T1. K+ : Na+ ratio, chlorophyll content, photosynthetic capacity, grain yield, flour yield, water absorbance, ash content, dough‐development time and dough‐stability time were significantly higher in T4 than in T3, while protein concentration, wet‐gluten concentration, and antioxidant enzyme activities were lower. Although foliar application of KNO3 on JN17 enhanced plant growth, grain yield, and grain quality, these parameters were still lower in T4 than in T1. Our findings suggest that cultivating the salt‐resistant wheat cultivar combined with foliar application of KNO3 at heading stage may alleviate salinity injuries and produce higher grain yield and better grain quality under saline conditions.

Responses of Halophyte Salicornia bigelovii to Different Forms of Nitrogen Source

Salt-affected soils are agricultural and environmental problems on a global scale. Plants suffer from saline stresses in these soils and show nitrogen (N) deficiency symptoms. However, halophytes grow soundly under saline conditions. In order to clarify the N nutrition of the halophyte Salicornia bigelovii, it was grown at several N levels (1, 2, 3, and 4 mmol L −1), supplied in the form of NO − 3 or ammonium (NH + 4), under high NaCl conditions (200 mmol L −1). NH + 4 -fed plants showed better growth than NO − 3 -fed plants at 1–3 mmol L −1 N, and plants in both treatments showed the same growth at 4 mmol L −1 N. Nitrogen contents in NO − 3 -fed plants increased with the N concentrations in solution; competitive inhibition of NO − 3 absorption by Cl − was observed under lower N conditions. In addition, shoot dry weight was significantly correlated only with shoot N content. Therefore, growth of NO − 3 -fed plants was regulated by N absorption. In contrast, N contents of shoots in NH + 4 -fed plants did not change with N concentration. Shoot Na content decreased with increasing N concentration, while K content increased. Dry weight was highly correlated only with K content in NH + 4 -fed plants. These observations indicated that growth of NH + 4 -fed plants was mainly regulated by K absorption.

In vitro salinity tolerance of two pistachio rootstocks: Pistacia vera L. and P. atlantica Desf

Seedlings of Pistacia vera L. and Pistacia atlantica Desf. were cultured on hormone-free DKW medium supplemented with NaCl. The plants were subjected to low NaCl concentrations ranging from 0 to 80 mM for 45 days or to high salt concentrations (0, 131, and 158.5 mM for P. vera and 0, 131, and 240 mM for P. atlantica) for 25 days. Toxicity symptoms were recorded for seedlings exposed to low NaCl treatments. Plant growth, survival rates, mineral content, as well as proline and soluble sugar contents were determined and evaluated at the end of the culture period. The results indicated that low NaCl treatments yielded no instances of plant death in both species. At high salt conditions, however, significant mortality rates were noted for both species, being 22.86% at 240 mM NaCl for P. atlantica and 25.8% at 158.5 mM NaCl for P. vera. With regards to salinity effects, levels of 60 and 80 mM NaCl induced significant decreases of stem elongation and leaf number in the P. vera species. Salinities between 40 and 80 mM NaCl, however, induced a decrease in the root number of both species. The fresh weights of P. vera and P. atlantica also decreased significantly after 45 days of culture at NaCl concentrations between 40 and 80 mM and after 25 days of culture at 158.5 and 240 mM NaCl, respectively. The sodium and chloride uptake in plant organs seemed to be controlled more efficiently in P. atlantica than in P. vera. In both species, the K + content was noted to undergo a significant decrease when salinity increased. While the K +/Na + ratio was maintained above 2 at low NaCl treatments, it was sharply decreased at high NaCl conditions, suggesting a failure of K–Na selectivity mechanism. The Ca 2+/Na + ratio decreased significantly at 60 and 80 mM NaCl in P. vera and at 60 mM NaCl for P. atlantica. In both Pistacia species, high NaCl treatments (131–240 mM NaCl) induced a significant increase in proline content.

Physiological aspects of Listeria monocytogenes during inactivation accelerated by mild temperatures and otherwise non-growth permissive acidic and hyperosmotic conditions

Application of simultaneous low pH (pH 3.5) and low water activity ( a w = 0.9; 2.5 M NaCl) conditions to Listeria monocytogenes strains ScottA and FW03/0035, and growth permissive temperatures from 25 °C up to 45 °C result in increasingly accelerated inactivation rates. This phenomenon was related to i) increased cell permeability as suggested by ethidium homodimer-1 uptake and ii) de-energization as indicated by rapidly reduced ATP basal levels. Enrichment-based recovery experiments indicated that the stress conditions eventually lead to complete loss of reproductive capacity, possibly corresponding to an irreversible collapse of pH homeostasis. Transcriptomic analyses were used to obtain further insights into the physiology of the inactivation process occurring at 25 °C where inactivation times were more prolonged. QPCR, mRNA decay and microarray experiments revealed transcripts of tufA and other genes become substantially more stable during inactivation resulting from exposure to combined low pH/ a w and from non-growth permissive temperature exposure. Genes that appear to be important for initial survival of combined low pH/ a w were delineated by K-means clustering of expression data and included an overrepresentation of SigB-activated genes, the overall response of which fades with increasing time of inactivation exposure.

Absence of direct effects on the dopamine D2 receptor by mGluR2/3‐selective receptor agonists LY 354,740 and LY 379,268

We previously reported the absence of high-affinity binding of the group II metabotropic glutamate receptor agonists LY 354,740 and LY 379,268 to the D2L dopamine receptor. A rebuttal to our findings has since been reported (see Introduction section); this study represents our response. Analysis by LCMS of LY 354,740 and LY 379,268 used in this study revealed the correct molecular mass for these compounds. Both LY 354,740 and LY 379,268 exhibited potent agonist activity for mGluR₂ in the ³⁵S-GTPγS assay. Functionally, neither compound displayed antagonist activity in the GTPγS assay with recombinant D₂. At concentrations up to 10 μM, both compounds failed to displace [³H]-raclopride, [³H]-PHNO, or [³H]-domperidone in filter-binding assays under isotonic (120 mM NaCl or N-methyl glucamine) or low-ionic strength (no NaCl or N-methyl glucamine) conditions. Some displacement of [³H]-domperidone (20-40%) was observed at 30 μM of LY 354,740 under low-ionic strength and under isotonic conditions in the absence of NaCl. No displacement of [³H]-domperidone was detected in a two site model at lower (<100 nM) concentrations of either compound. Moreover, no D₂ activity was observed for LY 354,740 or LY 379,268 in the CellKey™ (cellular dielectric spectroscopy) assay. In this communication, we discuss the possible reasons for differences in our study and the previously published work and implications of these studies for mechanisms of antipsychotic action.

Modulation of Responses of Vibrio parahaemolyticus O3:K6 to pH and Temperature Stresses by Growth at Different Salt Concentrations

Vibrio parahaemolyticus inhabits marine, brackish, and estuarine waters worldwide, where fluctuations in salinity pose a constant challenge to the osmotic stress response of the organism. Vibrio parahaemolyticus is a moderate halophile, having an absolute requirement for salt for survival, and is capable of growth at 1 to 9% NaCl. It is the leading cause of seafood-related bacterial gastroenteritis in the United States and much of Asia. We determined whether growth in differing NaCl concentrations alters the susceptibility of V. parahaemolyticus O3:K6 to other environmental stresses. Vibrio parahaemolyticus was grown at a 1% or 3% NaCl concentration, and the growth and survival of the organism were examined under acid or temperature stress conditions. Growth of V. parahaemolyticus in 3% NaCl versus that in 1% NaCl increased survival under both inorganic (HCl) and organic (acetic acid) acid conditions. In addition, at 42 degrees C and -20 degrees C, 1% NaCl had a detrimental effect on growth. The expression of lysine decarboxylase (encoded by cadA), the organism's main acid stress response system, was induced by both NaCl and acid conditions. To begin to address the mechanism of regulation of the stress response, we constructed a knockout mutation in rpoS, which encodes the alternative stress sigma factor, and in toxRS, a two-component regulator common to many Vibrio species. Both mutant strains had significantly reduced survival under acid stress conditions. The effect of V. parahaemolyticus growth in 1% or 3% NaCl was examined using a cytotoxicity assay, and we found that V. parahaemolyticus grown in 1% NaCl was significantly more toxic than that grown in 3% NaCl.

Cloning and Functional Characterization of a Novel Glutathione S-Transferase Gene from Limonium bicolor

Plant glutathione S-transferases (GSTs) are involved in protecting plants against both diverse biotic and abiotic stresses. In the present study, a novel GST gene (LbGST1) was cloned from Limonium bicolor (Bunge) Kuntze (Plumbaginaceae). To characterize its function in salt tolerance, tobacco lines transformed with LbGST1 were generated. Compared with wild-type (WT) tobacco, transgenic plants overexpressing LbGST1 exhibited both GST and glutathione peroxidase activities. Moreover, superoxide dismutase, peroxidase (POD), and catalase activities in transgenic plants were significantly higher than those in WT plants, particularly when grown under conditions of salt stress. Similarly, levels of proline in transgenic plants were also higher than those in WT plants grown under NaCl stress conditions. Whereas, Malondialdehyde contents in transgenic plants were lower than those in WT plants under NaCl conditions. Furthermore, Na+ content in transgenic plants was lower than that in WT plants under these stress conditions. Subcellular localization analysis revealed that the LbGST1 protein was localized in the nucleus. These results suggested that overexpression of LbGST1 gene can affect many physiological processes associated with plant salt tolerance. Therefore, we hypothesize that LbGST1 gene can mediate many physiological pathways that enhance stress resistance in plants.

Salt tolerance in Solanum pennellii: antioxidant response and related QTL

BackgroundExcessive soil salinity is an important problem for agriculture, however, salt tolerance is a complex trait that is not easily bred into plants. Exposure of cultivated tomato to salt stress has been reported to result in increased antioxidant content and activity. Salt tolerance of the related wild species, Solanum pennellii, has also been associated with similar changes in antioxidants. In this work, S. lycopersicum M82, S. pennellii LA716 and a S. pennellii introgression line (IL) population were evaluated for growth and their levels of antioxidant activity (total water-soluble antioxidant activity), major antioxidant compounds (phenolic and flavonoid contents) and antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and peroxidase) under both control and salt stress (150 mM NaCl) conditions. These data were then used to identify quantitative trait loci (QTL) responsible for controlling the antioxidant parameters under both stress and nonstress conditions.ResultsUnder control conditions, cultivated tomato had higher levels of all antioxidants (except superoxide dismutase) than S. pennellii. However, under salt stress, the wild species showed greater induction of all antioxidants except peroxidase. The ILs showed diverse responses to salinity and proved very useful for the identification of QTL. Thus, 125 loci for antioxidant content under control and salt conditions were detected. Eleven of the total antioxidant activity and phenolic content QTL matched loci identified in an independent study using the same population, thereby reinforcing the validity of the loci. In addition, the growth responses of the ILs were evaluated to identify lines with favorable growth and antioxidant profiles.ConclusionsPlants have a complex antioxidant response when placed under salt stress. Some loci control antioxidant content under all conditions while others are responsible for antioxidant content only under saline or nonsaline conditions. The localization of QTL for these traits and the identification of lines with specific antioxidant and growth responses may be useful for breeding potentially salt tolerant tomato cultivars having higher antioxidant levels under nonstress and salt stress conditions.

Amelioration of Salt Stress in Sugarcane ( Saccharum officinarum L.) by Supplying Potassium and Silicon in Hydroponics

A hydroponics experiment was conducted to evaluate the role of potassium (K) and silicon (Si) in mitigating the deleterious effects of NaCl on sugarcane genotypes differing in salt tolerance. Two salt-sensitive (CPF 243 and SPF 213) and two salt-tolerant (HSF 240 and CP 77-400) sugarcane genotypes were grown for six weeks in ½ strength Johnson's nutrient solution. The nutrient solution was salinized by two NaCl levels (0 and 100 mmol L −1 NaCl) and supplied with two levels of K (0 and 3 mmol L −1) and Si (0 and 2 mmol L −1). Applied NaCl enhanced Na + concentration in plant tissues and significantly ( P ≤ 0.05) reduced shoot and root dry matter in four sugarcane genotypes. However, the magnitude of reduction was much greater in salt-sensitive genotypes than salt-tolerant genotypes. The salts interfered with the absorption of K + and Ca 2+ and significantly ( P ≤ 0.05) decreased their uptake in sugarcane genotypes. Addition of K and Si either alone or in combination significantly ( P ≤ 0.05) inhibited the uptake and transport of Na + from roots to shoots and improved dry matter yields under NaCl conditions. Potassium uptake, K +/Na + ratios, and Ca 2+ and Si uptake were also significantly ( P ≤ 0.05) increased by the addition of K and/or Si to the root medium. In this study, K and Si-enhanced salt tolerance in sugarcane genotypes was ascribed to decreased Na + concentration and increased K + with a resultant improvement in K +/Na + ratio, which is a good indicator to assess plant tolerance to salt stress. However, further verification of these results is warranted under field conditions.

Principal component analysis of hormone profiling data suggests an important role for cytokinins in regulating leaf growth and senescence of salinized tomato

High throughput analytical methods allow phytohormonal profiling, but the magnitude of the data generated makes it difficult to draw firm conclusions about the physiological roles of different compounds. Principal Component Analysis (PCA) was used as a mathematical tool to evaluate relationships between physiological and hormonal variables in two experiments with salinized tomato. When tomato plants (cv Boludo F1) were grafted onto a recombined inbred line (RIL) population derived from a Solanum lycopersicum x S. cheesmaniae cross and grown under moderate salinity (75 mM NaCl) for 100 days under greenhouse conditions, PCA revealed an important role for leaf xylem cytokinins (CKs) in controlling leaf growth and photosystem II efficiency (Fv/Fm) and thus crop productivity under salinity. PCA analysis from a similar experiment, with ungrafted tomato grown under highly saline (100 mM NaCl) conditions, that evaluated the temporal sequence of leaf growth (as relative growth rate, LRGR) and senescence and hormone concentrations, revealed a similar influence of CKs on both processes, since Fv/Fm and LRGR were strongly loaded along the two principal components and placed in the same cluster as leaf trans-zeatin and/or related to other CK-related parameters. The conservative behaviour of the eigen vectors for Fv/Fm and the analysed phytohormones in different compartments (xylem, leaf and root) between different experiments suggests an important role for CKs in regulating leaf senescence, while CKs and other hormones seem to regulate leaf growth under salinity.

Effects of rhizobium strains isolated from wild chickpeas on the growth and symbiotic performance of chickpeas (Cicer arietinum L.) under salt stress

This study was conducted in order to evaluate the symbiotic effectiveness of Rhizobium leguminosarum bv. ciceri strains isolated from perennial wild chickpeas (Cicer anatolicum) in comparison to standard bacterial culture, N application, and uninoculated control under NaCl salinity stress conditions. For this purpose, 4 strains (DN1, DN7, TN3, and TN4) were obtained from wild chickpeas. Chickpea (Cicer arietinum L.) seeds were inoculated with these strains and grown in pots containing sterile sand under different levels of NaCl (0, 50, and 100 mM) in a controlled plant growth cabinet. Dry weights of root and shoot, root-to-shoot ratio (RSR), number and dry weights of nodules, chlorophyll and N content of the plant, and amounts of total and fixed N decreased progressively with increasing salinity levels. In both non-saline and saline (50 and 100 mM NaCl) conditions, inoculations with Rhizobium leguminosarum bv. ciceri strains isolated from wild chickpeas significantly increased all the above parameters compared with the uninoculated control treatment, equal to or higher than standard culture and N application. However, chickpea rhizobia exhibited diversity in their salt tolerance. The plants inoculated with DN7, TN4, and standard culture produced more shoot mass, nodule dry weight, total N, and fixed N under saline conditions, especially at 50 mM NaCl, than the plants inoculated with DN1 and TN3. These results indicated that the ability of chickpea to grow and survive in saline conditions improved when it was inoculated with Rhizobium leguminosarum bv. ciceri strains isolated from wild chickpeas, especially DN7 and TN4.

The low-salt stimulon in Vibrio parahaemolyticus

Vibrio parahaemolyticus is the leading cause of seafood-associated bacterial gastroenteritis and is a moderately halophilic, salt-requiring bacterium. Global gene expression profiles of V. parahaemolyticus grown under 2% and 0.66% NaCl were compared to define the low-salt stimulon. The ectABC-lysC operon for synthesis of the compatible solute ectoine, as well as three compatible solute transport systems, namely ProU (glycine betaine), OpuD1 (glycine betaine) and Pot2 (spermidine), was up-regulated under 2% NaCl relative to 0.66% NaCl. The 2% NaCl condition favored the inducible expression of OmpW, OmpN and OmpA2, while repressed the expression of OmpA1, OmpU and VP1008. These results indicated that, to master the hyperosmotic stress of saline environments, V. parahaemolyticus might not only accumulate osmoprotectants through uptake or endogenous synthesis of compatible solutes, but also remodel its profiles of outer membrane protein to restore its cell membrane. The above differentially regulated genes will provide novel candidates for the further investigation of the molecular mechanisms of osmoadaptation in V. parahaemolyticus.

Protection against diesel oil toxicity by sodium chloride-induced exopolysaccharides in Acinetobacter sp. strain DR1

Acinetobacter sp. strain DR1 is capable of growth on diesel oil. Interestingly, the degradation of diesel oil by the strain DR1 is enhanced in the presence of sodium chloride (NaCl). However, the growth rate of strain DR1 is not affected by the presence of NaCl. Northern blot analysis has also demonstrated that the effect of NaCl on the degradation of diesel oil is not attributable to increased levels of alkane hydroxylase (AlkM-type) gene expression. Rather, we have noted an increase in the exopolysaccharide (EPS) yields of strain DR1 under high NaCl conditions (9-fold). The lag-time of diesel oil biodegradation was significantly shorter in the strain DR1 with exogenous EPS than in the controls, although EPS alone does not support the growth of strain DR1. The recovery of strain DR1 when exposed to diesel oil was accelerated when exogenous EPS was added to the medium. The overproduction of EPS was also noted in the presence of diesel oil and n-hexadecane. The data indicated that EPS overproduction might play a protective role against diesel oil toxicity. Along with the results of the soil microcosm tests, the data presented herein demonstrated that NaCl-induced EPS is associated with a reduction in diesel oil toxicity, and thus increases diesel oil biodegradation in Acinetobacter sp. strain DR1.

Comparative effect of potassium on K and Na uptake and transport in two accessions of Arabidopsis thaliana during salinity stress

Potassium-sodium interaction was compared in two natural accessions of Arabidopsis thaliana, Columbia-0 and NOK2. Seedlings were grown in the presence of 0 or 50 mM NaCl and 0.1; 0.625 or 2.5 mM K +. At the lowest K + concentration, salt treatment inhibited both K + uptake and growth. Increasing the K + availability did not modified salt response in Columbia-0, but restored nearly normal net K + uptake in NaCl condition and alleviated NaCl growth reduction in NOK2. The effect of K + and NaCl on transcript level of several K + and Na + transporters in both shoots and roots was assessed using semi-quantitative RT-PCR. The mRNA abundance of the NHX1 and SOS1 Na +/H + antiporters was significantly increased by 50 mM NaCl in the two accessions. NHX1, which is responsible for Na + sequestration into vacuoles, was more up-regulated in NOK2 leaves than in Columbia-0's in NaCl stress condition. AKT1, which is the major channel involved in K + absorption, was down-regulated in salt stress condition, but was not responding to K + treatments. Only in NOK2 , SKOR and AKT2, which respectively control xylem and phloem K + transport, were markedly up-regulated by 2.5 mM K + in both roots and shoots, independently of NaCl. Phenotypic and gene expression analyses suggest that the relative salt tolerance of NOK2 is mainly due to a high ability to sequester Na + in the vacuole and to take up and transport K +. Up-regulation of SKOR and AKT2 by K +, and of NHX1 by NaCl could participate in determining this phenotype. To cite this article: R. Kaddour et al., C. R. Biologies 332 (2009).