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PubMed1997

DNA helix destabilization by proline and betaine: possible role in the salinity tolerance process.

Evidence is provided for the ability of proline, a salinity induced osmoprotectant, to destabilize the double helix and lower the Tm of DNA in a concentration dependent manner. At the reported salinity-adaptive bio-accumulation of 1 M and above, proline could considerably decrease the Tm and partially counteract the effect of sodium chloride and spermidine on DNA stability. On the contrary, several other amino acids tested did not show any such destabilizing effect on DNA helix. Enhanced susceptibility to S1 nuclease and insensitivity to DNase I in presence of increasing proline concentrations have further suggested a clear destabilization of the double helix. Such an effect is somewhat reminiscent of the interaction between betaine, another salinity induced osmolyte, and DNA resulting in decreased Tm values. These interactions may be significant in view of the abundance of such osmolytes in cells under salinity stress-adapted conditions, with many a bacterial mutant accumulating them exhibiting improved tolerance to salinity.

Amino Acids↗
PubMed1987

Gene induction and repression by salt treatment in roots of the salinity-sensitive Chinese Spring wheat and the salinity-tolerant Chinese Spring x Elytrigia elongata amphiploid.

An artificial amphiploid from a cross between salinity-sensitive bread wheat cultivar Chinese Spring and highly tolerant Elytrigia elongata (Host) Nevski (= Agropyron elongatum Host) shows enhanced salinity tolerance relative to Chinese Spring. Poly(A)(+) RNA was isolated from roots, expanding leaves, and old leaves from amphiploid and Chinese Spring plants prior to and after acclimation to high levels of NaCl in solution cultures. Two-dimensional gel electrophoresis of the in vitro translation products was used to compare these mRNA populations. The amphiploid had 10 mRNA species induced or enhanced and 8 species repressed in root tissue during acclimation to saline growth conditions. These 18 transcripts affected by salt treatment were also detected in wheat roots, but only 4 of these were similarly regulated. In Chinese Spring the acclimation to saline stress resulted in a marked change in the level of expression of 34 transcripts in root tissue; of these, 26 were detected in the amphiploid and only 6 were regulated as in the amphiploid. No differences were seen in gene expression between salt-treated and control plants in leaves and meristematic crowns and unexpanded leaves of the amphiploid.

Journal Article↗
PubMed1999

Transgenic overexpression of the transcription factor alfin1 enhances expression of the endogenous MsPRP2 gene in alfalfa and improves salinity tolerance of the plants

Alfin1 cDNA encodes a putative transcription factor associated with NaCl tolerance in alfalfa (Medicago sativa L.). The recombinant protein binds DNA in a sequence-specific manner, including promoter fragments of the NaCl-inducible gene MsPRP2. Alfin1 function was tested in transgenic alfalfa under the control of the 35S promoter in the sense and antisense orientations with the endogenous MsPRP2 as a reporter gene. Calli overexpressing Alfin1 were more resistant to growth inhibition by 171 mM NaCl than vector-transformed controls, whereas calli expressing Alfin1 in the antisense orientation were more sensitive to NaCl inhibition. Transgenic plants overexpressing Alfin1 in the sense orientation grew well. In contrast, the antisense transgenic plants grew poorly in soil, demonstrating that Alfin1 expression is essential for normal plant development. Transgenic calli and plant roots overexpressing Alfin1 showed enhanced levels of endogenous MsPRP2 mRNA accumulation. However, MsPRP2 mRNA accumulation was also regulated in a tissue-specific manner, as shown in leaves of transgenic plants overexpressing Alfin1. These results suggest that Alfin1 acts as a transcriptional regulator in plants and regulates MsPRP2 expression in alfalfa. Alfin1 overexpressing transgenic plants showed salinity tolerance comparable to one of our NaCl-tolerant plants, indicating that Alfin1 also functions in gene regulation in NaCl tolerance.

Journal Article↗
PubMed2006

Sub-lethal and chronic salinity tolerances of three freshwater insects: Cloeon sp. and Centroptilum sp. (Ephemeroptera: Baetidae) and Chironomus sp. (Diptera: Chironomidae).

Increased salinity in rivers and streams is a serious environmental concern, and in Australia there is growing information about the acute tolerances to salinity for freshwater macroinvertebrates, but much less information about chronic and sub-lethal tolerances. The effects of increased salinity on the growth and survival of two mayflies, Cloeon sp. and Centroptilum sp. and one midge Chironomus sp. are reported. In both mayfly species survival was variable. Complete mortality was observed in salinities with electrical conductivity of 10 mS cm(-1) and higher. Salinities causing chronic mortality in mayflies were measured as 21-day LC50, and ranged from 0.90 to 2.7 mS cm(-1). Growth rates were not significantly different between treatments. In Chironomus, salinity affected the mean number emerging as flying adults as well as the time to emergence. An inverted 'U' shape response was observed for percentage emergence, with the greatest numbers emerging at intermediate salinities (0.65-5.0 mS cm(-1)). No emergence occurred at salinities of 20 mS cm(-1) and higher. Time to emergence was delayed by 15-88% with increased salinity, however the size of emerged adults was the same for all treatments. Growth rates were reduced with increased salinity, showing a slow, steady reduction up to 10 mS cm(-1) then a steep decline between 10 and 15 mS cm(-1). The implications of altered growth rates and changes in developmental times are discussed. This study illustrates the variability in responses to increased salinity, and highlights the need to continue studying sub-lethal and chronic exposures in a range of freshwater invertebrates, in order to predict impacts of salinisation on freshwater biodiversity.

Animals↗
PubMed2005

Ontogeny of salinity tolerance and hyper-osmoregulation by embryos of the intertidal crabs Hemigrapsus edwardsii and Hemigrapsus crenulatus (Decapoda, Grapsidae): survival of acute hyposaline exposure.

The adults of Hemigrapsus edwardsii and Hemigrapsus crenulatus are euryhaline crabs and strong hyper-osmoregulators. Their embryos are carried externally attached to the abdominal pleopods of female crabs, where they are exposed to temporal and spatial changes in salinity associated with their intertidal and estuarine habitats. Although embryos lack the branchial and excretory organs responsible for adult osmoregulation, post-gastrula embryos were highly tolerant of exposure to hypo-osmotic sea water. Detached eggs (embryos+envelopes), of both species, at all developmental stages between gastrulation and hatching, exhibited 80-100% survival for periods up to 96 h in sea water (osmolality, 1050 mmol kg(-1)) and in dilutions to 50%, 10%, and 1%. Cleavage stages were less tolerant of dilution; H. edwardsii, <50% survived 24 h in 10% sea water; H. crenulatus <50% survived 6 h in 10% sea water. Post-gastrulation stages strongly hyper-osmoregulated but cleavage stages were hyper-osmoconformers (maintaining internal osmolality approximately 150 mmol kg(-1) above external). Osmoregulatory capacity was reduced just prior hatching, particularly in H. crenulatus, although salinity tolerance remained high. Gastrulation therefore marks a critical stage in the ontogeny of osmoregulation and salinity tolerance. Total Na+/K(+)-ATPase activity increased greatly during embryogenesis of H. crenulatus (undetectable in blastulae; gastrulae 0.31+/-0.05 pmol P(i) embryo(-1) min(-1); pre-hatching 16.4+/-1.0 pmol P(i) embryo(-1) min(-1)). Na+/K(+)-ATPase activity increased in embryos exposed to dilute sea water for 24 h implicating regulation of this transporter in a short-term acclimation response.

Acclimatization↗
PubMed2006

Salinity tolerance of 'Valencia' orange trees on rootstocks with contrasting salt tolerance is not improved by moderate shade.

The effects of shading in combination with salinity treatments were studied in citrus trees on two rootstocks with contrasting salt tolerance to determine if shading could reduce the negative effects of salinity stress. Well-nourished 2-year-old 'Valencia' orange trees grafted on Cleopatra mandarin (Cleo, relatively salt tolerant) or Carrizo citrange (Carr, relatively salt sensitive), were grown either under a 50% shade cloth or left unshaded in full sunlight. Half the trees received no salinity treatment and half were salinized with 50 mM Cl- during two 9 week salinity periods in the spring and autumn interrupted by an 11 week rainy period. The shade treatment reduced midday leaf temperature and leaf-to-air vapour pressure deficit regardless of salinity treatments. In non-salinized trees, shade increased midday CO2 assimilation rate (A(CO2)) and stomatal conductance, but had no effect on leaf transpiration (E(lf)). Shade also increased leaf chlorophyll and photosynthetic water use efficiency (A(CO2)/E(lf)) in leaves on both rootstocks and increased total plant dry weight in Cleo. The salinity treatment reduced leaf growth and leaf gas exchange parameters. Shade decreased Cl- concentrations in leaves of salinized Carr trees, but had no effect on leaf or root Cl- of trees on Cleo. There were no significant differences in leaf gas exchange parameters of shaded and unshaded salinized plants but the growth reduction from salinity stress was actually greater for shaded than for unshaded trees. Shaded trees on both rootstocks had higher leaf Na+ than unshaded trees after the first salinity period, and this shade-induced elevated leaf Na+ persisted after the second salinity period in trees on Carr. Thus, shading did not alleviate the negative effects of salinity on growth and Na+ accumulation.

Carbon Dioxide↗
PubMed1997

Salinity tolerances of selected macroinvertebrates of the Sabie River, Kruger National Park, South Africa.

Salinization has been identified as the most important problem facing the managers of South African freshwaters. Laboratory-based toxicity tests were conducted to assess the tolerance of selected macroinvertebrates to elevated salt concentrations. Since the Kruger National Park is the focus of river research in South Africa, and the Sabie River is the least mineralized river in the park, 96-h acute toxicity tests were conducted using Sabie River water and an ephemeropteran mayfly Tricorythus sp. found in the river. Experiments were conducted inflowing water systems known as raceways. The tolerance of the mayfly to two sodium salts, sodium chloride and sodium sulphate, was assessed at a range of selected conductivity levels/concentrations. The results indicated that mortality cannot be linked only to conductivity or total dissolved solid(TDS) concentrations, but also to the nature of the salt. Sodium sulphate was considerably more toxic to Tricorythus sp. than sodium chloride. Causes of mortality and implications for the development of water quality guidelines for the natural aquatic environment are discussed.

Animals↗
PubMed2002

Salinity tolerance and antioxidant status in cotton cultures.

This investigation focuses upon cell growth and antioxidant status in cultured cells of cotton (Gossypium herbaceum) cvs. Dhumad (salt-tolerant, TOL), H-14 (medium salt-tolerant, MED), and RAhs-2 (salt-sensitive, SEN) exposed to saline stress (50-200 mM NaCl). Mean (+/- SEM) callus fresh weight (f.wt.) and dry weight (d.wt.) gains were significantly (p <.05) greater on Murashige and Skoog (MS) [1]-based medium with 50 mM NaCl for the TOL cv. (62% and 16%, respectively) over NaCl-free controls (2020 +/- 45 and 166 +/- 4 mg, respectively); comparable differences were not observed for the MED cv. A significant (p <.05) decrease in mean f.wt. occurred with the SEN cv. exposed to 50 mM NaCl. For all cvs., there were (p <.05) reductions in mean f.wts. in medium with >or=100 mM NaCl. At 200 mM NaCl, mean f.wt. decreases were 52% (TOL), 89% (MED), and 91% (SEN), respectively. A strong correlation existed between antioxidant status and growth of cells with NaCl. Superoxide dismutase and glutathione reductase activities increased with increasing salinity in the TOL cv. to maximum values of 26.3 +/- 1.1 U mg(-1) protein and 1.05 +/- 0.01 AB(340 nm) min(-1) mg(-1) protein, respectively, at 150 mM NaCl; for the MED and SEN cvs., there were no changes in activities of these enzymes between control and salt treatments. Catalase activity decreased progressively with increasing salt concentration in all cvs. except for SEN with 100 mM NaCl, where mean catalase activity (1.75 +/- 0.04 AB(240 nm) min(-1) mg(-1) protein) was greater (p <.05) than control (1.13 +/- 0.08). Overall, cultured cotton cells provide an experimental system for investigating the role of antioxidants in salt tolerance at the cellular level.

Antioxidants↗
PubMed1986

Variation from plant tissue cultures: biotechnological application to improving salinity tolerance.

Breeding for salt tolerance in crop plants is envisaged as one way to combat a worldwide problem of increasing soil salinity in agricultural land. Tissue culture techniques may prove valuable as a means of achieving this goal. In this review, reports of the selection and characterization of plant cell cultures tolerant to excess salt are assessed, in the context of variability from tissue culture and the significance of cellular physiological adaptation to salinity. The examples of plant regeneration from salt grown cell cultures are also outlined, with emphasis on correlation to the effect of salt on cell cultures, genetic variability for salt tolerance in vitro, and the value of regenerates in the development of salt tolerant plants.

Journal Article↗
PubMed2005

Salinity tolerance in Daphnia magna: characteristics of genotypes hatching from mixed sediments.

The hatching of diapausing eggs is a means of temporal dispersal that can provide populations with genotypes adapted to different environments. In a salinity-variable shallow lake, we predicted that the mixing of different age-classes of eggs in the sediment may yield genotypes with different salinity optima. The alternative would be the absence of local adaptation and the presence of a homogenous population of salt-tolerant genotypes with high phenotypic plasticity. We tested these alternatives by isolating Daphnia magna resting eggs from different sediment depths, exposing them to hatching cues at different salinity levels and measuring the performance of hatched individuals. Results revealed a homogeneous sediment with generally broad-tolerance genotypes and some genotypes with low salt tolerance, which supports the second hypothesis. However, the disturbed character of the sediment hampered historical reconstruction. The absence of local adaptation in the diapausing egg bank may be the result of various scenarios in the response of D. magna populations to severe salinity changes in the lake.

Adaptation, Physiological↗
PubMed2025

Genome-wide characterization of ZmCRY genes: unveiling stress response mechanisms and the role of ZmCRYPHR2 in salinity tolerance.

BACKGROUND: Blue light serves as a crucial environmental signal regulating plant growth and development. The cryptochrome (CRY) family represents a key class of blue light receptors involved in these processes, as well as plant growth, development, and defense. However, the functions of CRYs in maize remain largely unexplored. RESULTS: In this study, nine ZmCRY genes were identified and found to be unevenly distributed across five chromosomes. Gene structure and conserved motif analyses revealed that ZmCRYs within the same phylogenetic groups are highly conserved. Synteny analysis indicated a close evolutionary relationship between ZmCRYs and their homologs in Oryza sativa. Promoter analysis identified diverse cis-regulatory elements linked to light response, stress tolerance, and hormone signaling. RT-qPCR analysis showed that ZmCRYs respond to various abiotic and biotic stresses, including high salinity, drought, nitrogen deficiency, Fusarium verticillioides, and Puccinia polysora. Functional studies demonstrated that ZmCRYPHR2, localized in chloroplasts and the cytoplasmic membrane, plays a role in scavenging reactive oxygen and regulating maize salt tolerance. Haplotype 2 of ZmCRYPHR2 was identified as the preferred haplotype in a panel of 269 inbred lines. CONCLUSIONS: These findings provide a comprehensive genomic and functional characterization of the ZmCRY gene family, with ZmCRYPHR2 identified as a pivotal regulator of salt tolerance, offering valuable genetic insights for the development of stress-resilient maize breeding.

Zea mays↗
PubMed1998

Regulation of cell-specific inositol metabolism and transport in plant salinity tolerance.

myo-Inositol and its derivatives are commonly studied with respect to cell signaling and membrane biogenesis, but they also participate in responses to salinity in animals and plants. In this study, we focused on L-myo-inositol 1-phosphate synthase (INPS), which commits carbon to de novo synthesis, and myo-inositol O-methyltransferase (IMT), which uses myo-inositol for stress-induced accumulation of a methylinositol, D-ononitol. The Imt and Inps promoters are transcriptionally controlled. We determined that the transcription rates, transcript levels, and protein abundance are correlated. During normal growth, INPS is present in all cells, but IMT is repressed. After salinity stress, the amount of INPS was enhanced in leaves but repressed in roots. IMT was induced in all cell types. The absence of myo-inositol synthesis in roots is compensated by inositol/ononitol transport in the phloem. The mobilization of photosynthate through myo-inositol translocation links root metabolism to photosynthesis. Our model integrates the transcriptional control of a specialized metabolic pathway with physiological reactions in different tissues. The tissue-specific differential regulation of INPS, which leads to a gradient of myo-inositol synthesis, supports root growth and sodium uptake. By inducing expression of IMT and increasing myo-inositol synthesis, metabolic end products accumulate, facilitating sodium sequestration and protecting photosynthesis.

Acclimatization↗
PubMed2025

Untargeted metabolomics reveals anion and organ-specific metabolic responses of salinity tolerance in willow.

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their tolerance remain poorly understood. Salix miyabeana was treated with two environmentally abundant salts, NaCl and Na2SO4, in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1&#x2009;dS&#x2009;m-1 soil ECe), maintaining biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- andin the canopy and adapting to osmotic stress via reduced stomatal conductance. Untargeted metabolomics captured >5000 putative compounds, including 278 core willow metabolome compounds constitutively produced across organs. Across all treatments, salinity drove widespread metabolic reprogramming, altering 28% of the overall metabolome, with organ-tailored strategies. Comparing salt forms at equimolar sodium, shared differentially abundant metabolites were limited to 3% of the metabolome, representing the generalised salinity response, predominantly in roots. Anion-specific metabolomic responses were extensive. NaCl reduced carbohydrates and tricarboxylic acid cycle intermediates, suggesting potential carbon and energy resource pressure, and accumulated root structuring compounds, antioxidant flavonoids, and fatty acids. Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting excess sulphate incorporation leverages ion toxicity to produce specialised salt-tolerance-associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ scale and considering ion-specific contributions to soil salinity.

Salix↗
PubMedDate not supplied

Salinity tolerance of Anopheles farauti Laveran sensu stricto.

To assess the salt tolerance of the malaria vector Anopheles farauti sensu stricto, larvae were collected from a freshwater environment on the outskirts of Honiara, Solomon Islands and placed in trays containing water with salinity varying from freshwater to seawater. Dead larvae and pupae and emerged adults were recorded and preserved. Most adults and nearly half of the larvae and pupae were then subjected to DNA analysis for species identification. No adult An. farauti emerged after prolonged immersion of larvae in undiluted seawater (3.5% salinity), although temporary immersion before pupation was compatible with survival. Salinities of up to 2.2% to 2.5% were compatible with good survival and adult emergence, at least from fourth instars. The results suggest that higher salinities may slow larval development and show that mortality at a given salinity is not uniform.

Animals↗
PubMed2000

Glycine betaine, carnitine, and choline enhance salinity tolerance and prevent the accumulation of sodium to a level inhibiting growth of Tetragenococcus halophila.

Natural-abundance (13)C-nuclear magnetic resonance was used to probe the intracellular organic solute content of the moderately halophilic bacterium Tetragenococcus halophila. When grown in complex growth media supplemented or not with NaCl, T. halophila accumulates glycine betaine and carnitine. Unlike other moderate halophiles, T. halophila was not able to produce potent osmoprotectants (such as ectoines and glycine betaine) through de novo synthesis when cultured in defined medium under hyperosmotic constraint. Addition of 2 mM carnitine, glycine betaine, or choline to defined medium improved growth parameters, not only at high salinity (up to 2.5 M NaCl) but also in media lacking NaCl. These compounds were taken up when available in the surrounding medium. The transport activity occurred at low and high salinities and seems to be constitutive. Glycine betaine and carnitine were accumulated by T. halophila in an unmodified form, while exogenously provided choline led to an intracellular accumulation of glycine betaine. This is the first evidence of the existence of a choline-glycine betaine pathway in a lactic acid bacterium. An assay showed that the compatible solutes strikingly repressed the accumulation of glutamate and slightly increased the intracellular potassium level only at high salinity. Interestingly, osmoprotectant-treated cells were able to maintain the intracellular sodium concentration at a relatively constant level (200 to 300 nmol/mg [dry weight]), independent of the NaCl concentration of the medium. In contrast, in the absence of osmoprotectant, the intracellular sodium content increased sharply from 200 to 2,060 nmol/mg (dry weight) when the salinity of the medium was raised from 1 to 2 M. Indeed, the imported compatible solutes play an actual role in regulating the intracellular Na(+) content and confer a much higher salt tolerance to T. halophila.

Adaptation, Physiological↗
PubMed2006

Effects of cyanobacterial extracellular products and gibberellic acid on salinity tolerance in Oryza sativa L.

Salt stress is one of the most serious factors limiting the productivity of rice, the staple diet in many countries. Gibberellic acid has been reported to reduce NaCl-induced growth inhibition in some plants including rice. Most paddy soils have a natural population of Cyanobacteria, prokaryotic photosynthethic microorganisms, which synthesize and liberate plant growth regulators such as gibberellins that could exert a natural beneficial effect on salt stressed rice plants. The aim of this work was to evaluate the effect of the cyanobacterium Scytonema hofmanni extracellular products on the growth of rice seedlings inhibited by NaCl and to compare it with the effect of the gibberellic acid in the same stress condition. Growth (length and weight of the seedlings) and biochemical parameters (5-aminolevulinate dehydratase activity, total free porphyrin and pigments content) were evaluated. Salt exposure negatively affected all parameters measured, with the exception of chlorophyll. Chlrorophyll concentrations nearly doubled upon exposure to high salt. Gibberellic acid counteracted the effect of salt on the length and dry weight of the shoot, and on carotenoid and chlorophyll b contents. Extracellular products nullified the salt effect on shoot dry weight and carotenoid content; partially counteracted the effect on shoot length (from 54% to 38% decrease), root dry weight (from 59% to 41% decrease) and total free porphyrin (from 31 to 13% decrease); reduced by 35% the salt increase of chlorophyll a; had no effect on root length and chlorophyll b. Gibberellic acid and extracellular products increased 5-aminolevulinate dehydratase activity over the control without salt. When coincident with high salinity, exposure to either EP or GA3, resulted in a reversal of shoot-related responses to salt stress. We propose that Scytonema hofmanni extracellular products may counteract altered hormone homeostasis of rice seedlings under salt stress by producing gibberellin-like plant growth regulators.

Journal Article↗
PubMed1993

Changes on protein expression associated with salinity tolerance in Brassica cell cultures.

The synthesis of proteins from salt-tolerant Brassica oleracea L. var. botrytis L. subvar. cauliflora (Gars.) DC. (cauliflower) cell cultures is modified in relation to controls in several features. There are nine newly induced polypeptides in tolerant cultures (absent in control conditions). Some of them are only present under low salt levels (85 mM NaCl). Another group seems to be representative of moderate and high salt levels (170 and 255 mM NaCl), and a third group is present in all the salt conditions tested. On the other hand, the synthesis of most of the polypeptides present in control conditions is modified in salt-tolerant cultures by increasing, decreasing or stopping their synthesis in any of the tested conditions. The relationship between these changes in Brassica and other plant systems is discussed.

Brassica↗