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PubMed2007

Molecular cloning of functional genes for high growth-temperature and salt tolerance of the basidiomycete Fomitopsis pinicola isolated in a mangrove forest in Micronesia.

Several functional genes encoding putative proteins, heat shock protein 70, sphingosine phosphate lyase, and Na+/H+ antiporter, were cloned from the basidiomycete Fomitopsis pinicola, a wood-rotting fungus isolated in the tropical mangrove forest of Pohnpei Island of the Federated States of Micronesia. The deduced amino acid sequences of the obtained genes involved in heat shock resistance, lipid synthesis, and salt tolerance showed diverse similarities to other homologous proteins. Molecular phylogenetic trees of these proteins suggested that encoded proteins of the cloned genes of F. pinicola differed remarkably from other homologs in various organisms, even fungal proteins. Putative candidates for other genes related to several cellular metabolisms were also amplified, implying the possible existence of those genes in F. pinicola. This is the first report of possibly functional genes derived from a basidiomycetous mushroom growing in tropical islands such as Micronesia. The genes found in this study might play important roles in the cellular survival of the basidiomycete F. pinicola under severe environmental conditions.

Amino Acid Sequence↗

PubMed1999

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl) sulfonate (PCS) Part I: Construction and characterization of the microbial sensor.

A microbial biosensor based on the yeast Arxula adeninivorans LS3 has been developed for measurement of biodegradable substances. Arxula is immobilized in the hydrogel poly(carbamoyl) sulfonate (PCS). The immobilized yeast membrane is placed in front of an oxygen electrode with -600 mV versus Ag/AgCl. Arxula is salt tolerant; it can give a stable signal up to 2.5 M NaCl in sample (120 mM in measuring cell). The sensor's measurements are highly correlated to BOD5 measurements. It has a very high stability which can last for 40 day without any decrease in signal. The linear range of the sensor is up to a corresponding BOD value of 550 mg/l.

Biodegradation, Environmental↗

PubMed2006

Cloning of an H+-PPase gene from Thellungiella halophila and its heterologous expression to improve tobacco salt tolerance.

An H(+)-pyrophosphatase (PPase) gene named TsVP involved in basic biochemical and physiological mechanisms was cloned from Thellungiella halophila. The deduced translation product has similar characteristics to H(+)-PPases from other species, such as Arabidopsis and rice, in terms of bioinformation. The heterologous expression of TsVP in the yeast mutant ena1 suppressed Na(+) hypersensitivity and demonstrated the function of TsVP as an H(+)-PPase. Transgenic tobacco overexpressing TsVP had 60% greater dry weight than wild-type tobacco at 300 mM NaCl and higher viability of mesophyll protoplasts under salt shock stress conditions. TsVP and AVP1, another H(+)-PPase from Arabidopsis, were heterologously expressed separately in both the yeast mutant ena1 and tobacco. The salt tolerance of TsVP or AVP1 yeast transformants and transgenic tobacco were improved to almost the same level. The TsVP transgenic tobacco lines TL3 and TL5 with the highest H(+)-PPase hydrolytic activity were studied further. These transgenic tobacco plants accumulated 25% more solutes than wild-type plants without NaCl stress and 20-32% more Na(+) under salt stress conditions. Although transgenic tobacco lines TL3 and TL5 accumulated more Na(+) in leaf tissues, the malondialdehyde content and cell membrane damage were less than those of the wild type under salt stress conditions. Presumably, compartmentalization of Na(+) in vacuoles reduces its toxic effects on plant cells. This result supports the hypothesis that overexpression of H(+)-PPase causes the accumulation of Na(+) in vacuoles instead of in the cytoplasm and avoids the toxicity of excessive Na(+) in plant cells.

Amino Acid Sequence↗

PubMed1998

A calcium sensor homolog required for plant salt tolerance.

Excessive sodium (Na+) in salinized soils inhibits plant growth and development. A mutation in the SOS3 gene renders Arabidopsis thaliana plants hypersensitive to Na+-induced growth inhibition. SOS3 encodes a protein that shares significant sequence similarity with the calcineurin B subunit from yeast and neuronal calcium sensors from animals. The results suggest that intracellular calcium signaling through a calcineurin-like pathway mediates the beneficial effect of calcium on plant salt tolerance.

Amino Acid Sequence↗

PubMed2006

Overexpressing a NAM, ATAF, and CUC (NAC) transcription factor enhances drought resistance and salt tolerance in rice.

Drought and salinity are major abiotic stresses to crop production. Here, we show that overexpression of stress responsive gene SNAC1 (STRESS-RESPONSIVE NAC 1) significantly enhances drought resistance in transgenic rice (22-34% higher seed setting than control) in the field under severe drought stress conditions at the reproductive stage while showing no phenotypic changes or yield penalty. The transgenic rice also shows significantly improved drought resistance and salt tolerance at the vegetative stage. Compared with WT, the transgenic rice are more sensitive to abscisic acid and lose water more slowly by closing more stomatal pores, yet display no significant difference in the rate of photosynthesis. SNAC1 is induced predominantly in guard cells by drought and encodes a NAM, ATAF, and CUC (NAC) transcription factor with transactivation activity. DNA chip analysis revealed that a large number of stress-related genes were up-regulated in the SNAC1-overexpressing rice plants. Our data suggest that SNAC1 holds promising utility in improving drought and salinity tolerance in rice.

Abscisic Acid↗

PubMed2006

Ectopic expression of ThCYP1, a stress-responsive cyclophilin gene from Thellungiella halophila, confers salt tolerance in fission yeast and tobacco cells.

The halophyte Thellungiella halophila (salt cress) is an ideal model system for studying the molecular mechanisms of salinity tolerance in plants. Herein, we report the identification of a stress-responsive cyclophilin gene (ThCYP1) from T. halophila, using fission yeast as a functional system. The expression of ThCYP1 is highly inducible by salt, abscisic acid (ABA), H(2)O(2) and heat shock. Ectopic overexpression of the ThCYP1 gene enhance the salt tolerance capacity of fission yeast and tobacco (Nicotiana tabacum L.) cv. Bright Yellow 2 (BY-2) cells significantly. ThCYP1 is expressed constitutively in roots, stems, leaves and flowers, with higher expression occurring in the roots and flowers. The ThCYP1 proteins are distributed widely within the cell, but are enriched significantly in the nucleus. The present results suggest that ThCYP1 may participate in response to stresses in the salt cress, perhaps by regulating appropriate folding of certain stress-related proteins, or in the signal transduction processes.

Abscisic Acid↗

PubMed2006

Role of oxidative stress in the extremely salt-tolerant yeast Hortaea werneckii.

Eukaryotic halotolerant microorganisms are important as model organisms to understand the general mechanisms of resistance to environmental salinity. The ability of the extremely halotolerant black yeast Hortaea werneckii to combat oxidative stress was addressed, using hydrogen peroxide to generate the reactive oxygen species. Increasing environmental salinity was found to have no effect on its high ability to degrade hydrogen peroxide but resulted in a decrease in viability in response to externally added hydrogen peroxide, suggesting that the latter property determines the upper limit of the salt tolerance of H. werneckii. A refinement of the model of adaptation of H. werneckii to high-salinity environments is proposed.

Adaptation, Physiological↗

PubMed2005

Identification of conserved polar residues important for salt tolerance by the Na+/H+ exchanger of Schizosaccharomyces pombe.

The Na+/H+ exchanger is a ubiquitous protein that transports Na+ and H+ in opposite directions across cell membranes. In fission yeast, the Na+/H+ exchanger sod2 plays a major role in the removal of excess detrimental intracellular sodium. The effect of mutagenesis of conserved polar amino acids of sod2 was examined by expressing 10 different mutant forms of sod2 in sod2 deficient S. pombe and characterizing salt tolerance. Asp145, 266, 267, and Glu173 were critical for proper function of sod2. Asp241 had an intermediate effect on sod2 function while mutation of Asp178 did not impair sod2 function. Simultaneous mutation of the Asp266, 267 pair impaired sod2 function. Mutation of each individual residue demonstrated that both were critical for sod2 function. Conservative mutations (Asp to Glu) of Asp266 and 267 failed to restore sod2 function. The results suggest that acidic residues associated with transmembrane segments are important in function, possibly being important in binding and coordinating cations.

Amino Acid Substitution↗

PubMed2001

Salt tolerance of Triticum monococcum L., T. dicoccum (Schrank) Schubl., T. durum Desf. and T. aestivum L. seedlings.

Responses to salt stress of diploid wheat Triticum monococcum L., tetraploid wheats T. dicoccum (Schrank) Schubl. and T. durum Desf. cv. Grandur, and hexaploid wheats T. aestivum L. cvs. Begra and Gama were studied. Seeds were germinated on filter paper in Petri dishes, moistened in Hoagland medium containing 0 (control), 10, 20, 50, 100 and 200 mM NaCl. Index of tolerance to salt treatments was calculated on the basis of shoot length. Increase in salt concentration led to decrease in seed germination and inhibition of shoot and root elongation. Hexaploid and diploid wheats were more tolerant to salt stress than tetraploid wheats.

Journal Article↗

PubMed2005

Disruption of a gene encoding glycerol 3-phosphatase from Candida albicans impairs intracellular glycerol accumulation-mediated salt-tolerance.

Intracellular glycerol accumulation is critical for Candida albicans to maintain osmolarity, and therefore defects in glycerol homeostasis can have severe effects on the morphogenetic plasticity and pathogenicity of this fungus. The final step of glycerol synthesis involves the dephosphorylation of glycerol 3-phosphate by glycerol 3-phosphatase (GPP1). We have identified a single copy of the GPP orthologous gene (GPP1) in the C. albicans haploid genome, as well as the paralogous gene 2-deoxyglucose-6-phosphate phosphatase (DOG1); both belong to a family of low molecular weight phosphatases. A knockout of the GPP1 gene in C. albicans caused increased susceptibility to high salt concentrations, indicating a deficiency in osmoregulation. Reintroduction of the GPP1 gene complemented the impairment of salt-tolerance in the gpp1/gpp1 mutant. Northern blot analysis showed that the GPP1 gene was strongly responsive to osmotic stress, and its transcriptional expression was positively correlated with intracellular glycerol accumulation. These results demonstrate that the GPP1 gene plays an important role in the osmoregulation in C. albicans.

Amino Acid Sequence↗

PubMedDate not supplied

Salt-tolerant and thermostable alkaline protease from Bacillus subtilis NCIM no. 64.

The proteolytic activity produced by a Bacillus subtilis isolated from a hot spring was investigated. Maximum protease production was obtained after 38 h of fermentation. Effects of various carbon and nitrogen sources indicate the requirement of starch and bacteriological peptone to be the best inducers for maximum protease production. Requirement for phosphorus was very evident, and the protease was secreted over a wide range of pH 5-11. The partially purified enzyme was stable at 60 degrees C for 30 min. Calcium ions were effective in stabilizing the enzyme, especially at higher temperature. The enzyme was extremely salt tolerant and retained 100% activity in 5M NaCl over 96 h. The molecular weight of the purified enzymes as determined by SDS-PAGE was 28,000. The enzyme was completely inactivated by PMSF, but little affected by urea, sodium dodecyl sulfate, and sodium tripoly phosphate.

Bacillus subtilis↗

PubMed2001

Drought- and salt-tolerant plants result from overexpression of the AVP1 H+-pump.

Transgenic plants overexpressing the vacuolar H(+)-pyrophosphatase are much more resistant to high concentrations of NaCl and to water deprivation than the isogenic wild-type strains. These transgenic plants accumulate more Na(+) and K(+) in their leaf tissue than the wild type. Moreover, direct measurements on isolated vacuolar membrane vesicles derived from the AVP1 transgenic plants and from wild type demonstrate that the vesicles from the transgenic plants have enhanced cation uptake. The phenotypes of the AVP1 transgenic plants suggest that increasing the vacuolar proton gradient results in increased solute accumulation and water retention. Presumably, sequestration of cations in the vacuole reduces their toxic effects. Genetically engineered drought- and salt-tolerant plants could provide an avenue to the reclamation of farmlands lost to agriculture because of salinity and a lack of rainfall.

Abscisic Acid↗

PubMed2005

How to be moderately halophilic with broad salt tolerance: clues from the genome of Chromohalobacter salexigens.

We analyzed the amino acid composition of different categories of proteins of the moderately halophilic bacterium Chromohalobacter salexigens, as deduced from its genome sequence. Comparison with non-halophilic representatives of the gamma-Proteobacteria (Escherichia coli, Pseudomonas aeruginosa, Vibrio cholerae) shows only a slight excess of acidic residues in the cytoplasmic proteins, and no significant differences were found in the acidity of membrane-bound proteins. In contrast, a very pronounced difference in mean pI value was observed for the periplasmic binding proteins of the ABC transport systems of C. salexigens and the non-halophiles E. coli and P. aeruginosa. V. cholerae, which is adapted to life in brackish water, showed intermediate values. The findings suggest that there is a major difference between the proteins of the moderate halophile C. salexigens and non-halophilic bacteria in their periplasmic proteins, exemplified by the substrate binding proteins of transport systems. The highly acidic nature of these proteins may enable them to function at high salt concentrations. The evolution of highly salt-tolerant prokaryotes may have depended on an increase in acidity of the proteins located external to the cytoplasmic membrane, enabling effective transport of nutrients into the cell.

Amino Acids↗

PubMed2002

An osmotically induced cytosolic Ca2+ transient activates calcineurin signaling to mediate ion homeostasis and salt tolerance of Saccharomyces cerevisiae.

Hyperosmotic stress caused by NaCl, LiCl, or sorbitol induces an immediate and short duration ( approximately 1 min) transient cytosolic Ca(2+) ([Ca(2+)](cyt)) increase (Ca(2+)-dependent aequorin luminescence) in Saccharomyces cerevisiae cells. The amplitude of the osmotically induced [Ca(2+)](cyt) transient was attenuated by the addition of chelating agents EGTA or BAPTA, cation channel pore blockers, competitive inhibitors of Ca(2+) transport, or mutations (cch1Delta or mid1Delta) that reduce Ca(2+) influx, indicating that Ca(ext)(2+) is a source for the transient. An osmotic pretreatment (30 min) administered by inoculating cells into media supplemented with either NaCl (0.4 or 0.5 m) or sorbitol (0.8 or 1.0 m) enhanced the subsequent growth of these cells in media containing 1 m NaCl or 2 m sorbitol. Inclusion of EGTA in the osmotic pretreatment media or the cch1Delta mutation reduced cellular capacity for NaCl but not hyperosmotic adaptation. The stress-adaptive effect of hyperosmotic pretreatment was mimicked by exposing cells briefly to 20 mm CaCl(2). Thus, NaCl- or sorbitol-induced hyperosmotic shock causes a [Ca(2+)](cyt) transient that is facilitated by Ca(2+) influx, which enhances ionic but not osmotic stress adaptation. NaCl-induced ENA1 expression was inhibited by EGTA, cch1Delta mutation, and FK506, indicating that the [Ca(2+)](cyt) transient activates calcineurin signaling to mediate ion homeostasis and salt tolerance.

Calcineurin↗

PubMed2004

Analysis of gene network regulating yeast multidrug resistance by artificial activation of transcription factors: involvement of Pdr3 in salt tolerance.

We established a strategy to constitutively activate Zn(2)Cys(6)-type protein by fusing its DNA-binding domain with the VP16 trans-activation domain. To explore gene network regulating yeast multidrug resistance, the strategy was applied to Pdr1, Pdr3 and Yrr1, known to regulate multidrug resistance, as well as three uncharacterized Yrr1-related transcription factors. DNA microarray analysis revealed that all of the six mutants induce typical drug transporter genes including SNQ2 and YOR1, suggesting redundancy in regulation. On the other hand, each displays a unique spectrum of targets, which is coincident with the phylogenetic tree of the transcription factors and presumably reflects their functional specification. Indeed, careful analysis of target genes specific to each transcription factor led us to reveal an unexpected role for Pdr3 in salt tolerance. The strategy would thus contribute not only to identify target genes but to reveal redundancy and specificity in complex gene regulatory networks.

ATP-Binding Cassette Transporters↗

PubMed2000

Theasaponin E1 destroys the salt tolerance of yeasts.

Cells of Zygosaccharomyces rouxii in a medium containing a high concentration of NaCl were killed during incubation for 2-4 h with a low concentration of a mixture of saponins from tea seeds (TSS). The higher the concentration of NaCl in the medium, the higher the inhibitory effect of TSS on the growth of the yeast. The above inhibitory effect of TSS on the growth of the yeast was not observed when cells were incubated in hypertonic media composed of nonionic substances such as sugars. The ATPase activity of plasma membrane preparations from the yeast cells was slightly affected by the addition of TSS. It is shown that TSS facilitates leakage of glycerol from the yeast cells under NaCl-hypertonic conditions. The major inhibitor in the mixture of saponins was isolated and identified as theasaponin E1. Its isomer, theasaponin E2, did not have any effect on the salt tolerance of Z. rouxii or Saccharomyces cerevisiae.

Journal Article↗

PubMed2002

Salt-tolerant ATPase activity in the plasma membrane of the marine angiosperm Zostera marina L.

Plasma membrane (PM) H(+)-ATPase and H(+) transport activity were detected in PM fractions prepared from Zostera marina (a seagrass), Vallisneria gigantea (a freshwater grass) and Oryza sativa (rice, a terrestrial plant). The properties of Z. marina PM H(+)-ATPase, specifically, the optimal pH for ATPase activity and the result of trypsin treatment, were similar to those of authentic PM H(+)-ATPases in higher plants. In V. gigantea and O. sativa PM fractions, vanadate-sensitive (P-type) ATPase activities were inhibited by the addition of NaCl. In contrast, activity in the Z. marina PM fraction was not inhibited. The nitrate-sensitive (V-type) and azide-sensitive (F-type) ATPase activities in the Z. marina crude microsomal fraction and the cytoplasmic phosphoenolpyruvate carboxylase activity, however, were inhibited by NaCl, indicating that not all enzyme activities in Z. marina are insensitive to salt. Although the ratio of Na(+) to K(+) (Na(+)/K(+)) in seawater is about 30, Na(+)/K(+) in the Z. marina cells was about 1.0. The salt-tolerant ATPase activity in the plasma membrane must play an important role in maintaining a low Na(+) concentration in the seagrass cells.

Adaptation, Physiological↗

PubMed1998

In Vitro Propagation of Salt-Tolerant Wild Rice Relative, Porteresia coarctata Tateoka.

Micropropagation of Porteresia coarctata Tateoka, a wild relative of rice with useful genetic traits of salinity and submergence tolerance, was achieved through nodal segment culture. Woody Plant (WP) medium supplemented with benzyladenine (5.5 µm) and kinetin (2.3 µm) gave the greatest response to initiation and multiplication. The multiplication rate of 11 shoots/explant with an average shoot length of 3.5 cm was observed after 8 weeks of culture period. The rooting response was observed simultaneously in the multiplication media, but subsequent establishment was poor. When the in vitro raised shoots were transferred to optimal 1/2 WP and 1/2 MS media with 10.7 µm alpha-naphthaleneacetic acid, the rooting response was enhanced. Such rooted plants were hardened successfully under field conditions. Key Words. Conservation-Mangrove associates-Micropropagation-Nodal explants-Porteresia coarctata-Salt tolerance

Journal Article↗