Comprehensive evaluation of salt-alkali tolerance of rice germplasms at germination and seedling stages and analysis of salt-tolerant genes / 生物工程学报

Cultivating salt-alkali tolerant rice varieties is one of the important ways to meet the increasing food demand of growing global population. In this study, twenty-one rice germplasms with different salt-alkali tolerance were treated with six salt-alkali concentrations at germination and seedling stages. The germination potential, germination rate, shoot length, root length, root number, fresh weight of shoot and seedlings were measured. The average value of salt damage rate was used to evaluate the salt-alkali tolerance. As the salt-alkali concentration increases, the inhibition on seed germination and growth became more obvious. Upon treatment with 1% NaCl plus 0.25% NaHCO3, the salt damage rate of germination rate has the largest variation, ranging from 0% to 89.80%. The salt damage rate of each trait shows a similar trend at all concentrations. Four germplasm resources with strong salt-alkali tolerance (Dajiugu, Nippobare, Mowanggu and 02428) and 7 sensitive germplasms were screened. The salt-tolerant gene sequence of 4 salt-alkali tolerant varieties and 3 sensitive germplasms were analyzed. OSHAL3 and OsRR22 were identical among the 7 germplasms, but SKC1 and DST showed clear variations between the salt-alkali tolerant and sensitive germplasms. Besides the salt-alkali tolerant germplasm resources, this study can also serve as a reference for mining of genes involved in salt-alkali tolerance and breeding of salt-alkali tolerant rice varieties.

Screening and evaluation of saline-alkali-tolerant and growth-promoting bacteria / 生物工程学报

Salinity is the most important factor for the growth of crops. It is an effective method to alleviate the toxic effect caused by salt stress using saline-alkali-tolerant and growth-promoting bacteria in agriculture. Seven salt-tolerant bacteria were screened from saline-alkali soil, and the abilities of EPS production, alkalinity reduction and IAA production of the selected strains were investigated. A dominant strain DB01 was evaluated. The abilities of EPS production, alkalinity reduction and IAA production of strain DB01 were 0.21 g/g, 8.7% and 8.97 mg/L, respectively. The isolate was identified as Halomonas aquamarina by partial sequencing analysis of its 16S rRNA genes, and had the ability to inhibit the growth of Fusarium oxysporum f. sp., Alternaria solani, Phytophthora sojae and Rhizoctonia cerealis. It also could promote root length and germination rate of wheat seedlings under salt stress. Halomonas aquamarina can provide theoretical basis for the development of soil microbial resources and the application in saline-alkali soil improvement.

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 salt stress, the yeast Debaryomyces hansenii synthesizes tyrosine as a strategy to avoid the oxidation of proteins. Tyrosine reacts with nitrogen radicals to form 3-nitrotyrosine. 3-nitrotyrosine prevents the effects of associated oxidative stress and thus contributes to the high halotolerace of the yeast. However, the mechanism of how D. hansenii counteracts the presence of this toxic compound is unclear. In this work, we evaluated D. hansenii's capacity to assimilate 3-nitrotyrosine as a unique nitrogen source and measured its denitrase activity under salt stress. 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 promoters had binding site 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, were evaluated by RT-PCR and showed high expression under salt and nitrogen stress. Conclusions: D. hansenii can grow in the presence of 3-nitrotyrosine as the only nitrogen source and has a high specific denitrase activity to degrade 3-nitrotyrosine in 1 and 2 M NaCl stress conditions. The results suggest that given the lack of information on transcriptional factors in D. hansenii, the genes identified in our in silico analysis may help explain 3-nitrotyrosine assimilation mechanisms.

Regulation of nitrogen metabolism in salt tolerant and salt sensitive Frankia strains.

Effect of salinity (0, 50, 100, 250, 500 and 750 mM NaCl) was observed on some important physiological parameters of nitrogen metabolism such as nitrate uptake, intracellular and extracellular ammonium status and activities of nitrogenase, nitrate reductase, nitrite reductase and glutamine synthetase among Frankia strains differing in their salt tolerance capacity. Nitrogenase activity closely followed the growth pattern with regular decline on NaCl supplementation. All the other enzymes showed optimum activity at 100 mM and declined further. Co-regulation of the nitrate uptake system and sequential enzyme activities plays a crucial role in governing the nitrogen status of strains during salt stress. HsIi10 experiencing minimum decline in enzyme activities and best possible nitrogen regulation under NaCl replete condition showed adequate nutritional management. Among all the strains, HsIi10 proved to be salt tolerant on account of above features while the salt sensitive strain HsIi8 lacked the ability to regulate various steps of nitrogen metabolism during salinity, and thus Frankia strain HsIi10 can potentially serve as a potential biofertilizer in the saline soil.

In vitro mutation induced by ethylmethane sulfonate in Stevia rebaudiana and SRAP identification of salt-tolerant mutants / 中草药

Objective: The in vitro mutation system of Stevia rebaudiana induced by ethylmethane sulfonate (EMS) was established, and the salt-tolerant mutants were identified by SRAP. Methods: S. rebaudiana plantlets were inoculated on MS media containing NaCl with different concentration to screen the salt-tolerant critical concentration. Plantlets were treated with EMS at different concentration and for different time periods, and EMS mutagenized stems were inoculated on MS medium containing critical NaCl concentration to screen the tolerant variants by SRAP markers. Results: The critical salt concentration of S. rebaudiana plantlets was 1.0%, and the suitable concentration and time of EMS were 0.8%-1.0% and 8-10 h. Among the screened 41 S. rebaudiana tolerant mutants by SRAP molecular markers, four were mutated at DNA level, and the mutation rate was 9.76%. Conclusion: The in vitro mutagenesis system of S. rebaudiana with EMS has been established, which provides a new breeding way for high-yield salt-tolerant S. rebaudiana.

Optimization studies on production of a salt-tolerant protease from Pseudomonas aeruginosa strain BC1 and its application on tannery saline wastewater treatment

Treatment and safe disposal of tannery saline wastewater, a primary effluent stream that is generated by soaking salt-laden hides and skin is one of the major problems faced by the leather manufacturing industries. Conventional treatment methods like solar evaporation ponds and land composting are not eco-friendly as they deteriorate the ground water quality. Though, this waste stream is comprised of high concentration of dissolved proteins the presence of high salinity (1-6 percent NaCl by wt) makes it non-biodegradable. Enzymatic treatment is one of the positive alternatives for management of such kind of waste streams. A novel salt-tolerant alkaline protease obtained from P.aeruginosa (isolated from tannery saline wastewater) was used for enzymatic degradation studies. The effect of various physical factors including pH, temperature, incubation time, protein source and salinity on the activity of identified protease were investigated. Kinetic parameters (Km , Vmax) were calculated for the identified alkaline protease at varying substrate concentrations. Tannery saline wastewater treated with identified salt tolerant protease showed 75 percent protein removal at 6 h duration and 2 percent (v/v) protease addition was found to be the optimum dosage value.

Secretion of an alkaline protease from a salt- tolerant and alkaliphilic, Streptomyces clavuligerus strain Mit-1

An alkaliphilic and salt- tolerant actinomycete, Streptomyces clavuligerus strain Mit-1, was isolated from Mithapur, the western coast of India. The organism was Gram-positive, having filamentous, long thread like structure. The sporulation started after two days of growth and the optimum level of alkaline protease (130 U/ml) was produced during the early stationary phase. The strain could grow and produce protease with 0-10 percent NaCl (w/v), the optimum being 5 percent NaCl (w/v). Growth and protease production was optimum at pH 9 with substantial decline at neutral pH. Sucrose and gelatin were the best carbon and nitrogen sources respectively, whereas gelatin broth was the preferred medium for protease production. Mit-1 produced substantial protease with various amino acids, when employed as the sole nitrogen sources. Crude substrates, such as molasses, whey and wheat flour had significant effect on enzyme production. The results are quite valuable, as only few actinomycetes, particularly salt-tolerant alkaliphilic ones, have so far been explored for their enzymatic potential and process optimization.

Uma cepa halotolerante e alcalifílica de Streptomyces clavuligerus, Mit-1, foi isolada em Mithapur, na costa oeste da Índia. Esse microrganismo é Gram positivo e apresenta estrutura filamentosa na forma de longas cordas. A esporulação iniciou após dois dias de cultivo e o nível ótimo de produção de protease alcalina (130 U/ml) foi atingido no início da fase estacionária de crescimento. A cepa foi capaz de multiplicar com 0-10 por cento NaCl (w/v), com um ótimo de 5 por cento NaCl (w/v). O ótimo de crescimento e produção de protease foi atingido em pH 9, apresentando declínio substancial em pH neutro. Sacarose e gelatina foram as melhores fones de carbono e nitrogênio, respectivamente, enquanto o caldo gelatina foi o melhor meio para produção de protease. A cepa Mit-1 produziu bastante protease quando vários aminoácidos foram empregados como única fonte de nitrogênio. Substratos crus, como melaço, soro de leite e farinha de trigo, tiveram um efeito significativo na produção da enzima. Os resultados são bastante interessantes, considerando que somente poucos actinomicetos, especialmente os halotolerantes, já foram explorados por seu potencial de produção de enzimas e otimização de processos.

Isolation and Characteristic of an Azo Dye-decolorizing Salt-tolerant Bacteria Strain GYW / 微生物学通报

A salt-tolerant strain GYW capable of decolorating azo dye was isolated and identified as Halo-monas sp.by 16S rDNA.The result showed that the decolorizing salt-tolerant bacteria could survive above the 10% salt concentration and it could decolorize many dyes.The strain had a high decolorizing rate on acid red GR under the condition of pH 7.5,anaerobic 30?C and 10% NaCl.The ion of Cl- strong inhibited the decolorization of acid red GR,and the ion of SO42- affected little on the decolorization,and the lycine addi-tion with the optimal concentration of 200 mg/L could enhanced the decolorization rate under high NaCl concentration.