Level Of Salt Tolerance Research Articles

Novel Salt-Tolerant Xylanase from a Mangrove-Isolated Fungus Phoma sp. MF13 and Its Application in Chinese Steamed Bread.

A novel glycosyl hydrolase family 11 xylanase gene, xynMF13A, was cloned from Phoma sp. MF13, a xylanase-producing fungus isolated from mangrove sediment. xynMF13A was heterologously expressed in Pichia pastoris, and the recombinant XynMF13A (rXynMF13A) was purified by Ni-affinity chromatography. The temperature and pH optima of purified rXynMF13A were 45 °C and pH 5.0, respectively. rXynMF13A showed a high level of salt tolerance, with maximal enzyme activity being seen at 0.5 M NaCl and as much as 53% of maximal activity at 4 M NaCl. The major rXynMF13A hydrolysis products from corncob xylan were xylobiose, xylotriose, xylotetraose, and xylopentaose, but no xylose was found. These hydrolysis products suggest an important potential for XynMF13A in the production of xylooligosaccharides (XOs). Furthermore, rXynMF13A had beneficial effects on Chinese steamed bread production, by increasing specific volume and elasticity while decreasing hardness and chewiness. These results demonstrate XynMF13A to be a novel xylanase with potentially significant applications in baking, XOs production, and seafood processing.

Phenotypic and genotypic screening of rice genotypes at reproductive stage for salt tolerance

Salinity screening of 24 rice genotypes was performed at the reproductive stage for evaluating their salt tolerance level. On the basis of yield and yield components, genotypes were categorized as tolerant, susceptible and moderately tolerant. PBRC-30, Ashfal, Horkuch, STL-20 and Pokkali were found as tolerant while Binadhan-7, S-39 L-11, S-37 L- 27, S-37 L-36 and S-37 L-39 were found as susceptible. Selected three SSR markers viz. RM336, RM21 and RM510 were used to determine salinity tolerance. The genetic diversity was ranges from 0.8194 to 0.8854 with an average of 0.8530. The highest PCI value was 0.8742 and the lowest was 0.8004 from RM510 and RM21, respectively. The UPGMA clustering system generated six genetic clusters. The highest genetically dissimilarity of (Cluster 1) vs (Cluster 2 sub-cluster A) and the crossing would be helpful for salt tolerant rice development. Thus, selected SSR primers and genotypes would be useful in marker assisted breeding, quantitative trait loci (QTL) mapping and gene pyramiding in breeding programmed for improvement of rice for salt tolerance.SAARC J. Agri., 15(2): 69-80 (2017)

Relation between level of autumn dormancy and salt tolerance in lucerne (Medicago sativa)

Experiments were conducted to study the relationship between autumn (fall) dormancy rating (FDR) and salt tolerance of lucerne (alfalfa, Medicago sativa L.). Seeds of eight cultivars with different FDRs (range 2.0–10.2) were germinated in a growth chamber under five concentrations of NaCl (range 0–1.2%). A subordinate function value method was adopted for comprehensive evaluation of salt tolerance of the lucerne cultivars. Seed germination rate and germination potential, and seedling electrolyte leakage, shoot length, root length, fresh weight, root : shoot length ratio, Na+ and K+ concentrations and K+ : Na+ ratio were used as the indices of evaluation. Under 1.2% salt treatment, salt-tolerance ranking of the cultivars was WL656HQ > WL440HQ > WL712HQ > WL525HQ > WL343HQ > WL319HQ > WL363HQ > WL168HQ, with respective FDRs of 9.3, 6.0, 10.2, 8.2, 3.9, 2.8, 4.9 and 2.0. The results of this study show that non-dormant cultivars were generally more salt tolerant than dormant cultivars.

Effects of Salinity Stress on Emergence and Seedling Growth Parameters of Some Maize Genotypes (Zea mays L.)

Maize is a very important cereal all over the world and generally cultivated in irrigated agricultural areas. Salinity affects adversely maize productivity in these areas. Maize is known as a salt sensitive species. The salt tolerance level identification in the large genetic resources and breeding populations is an important research topic for solving the salinity problem. The effects of NaCl stress on germination and seedling growth of fifteen maize genotypes were investigated in this study. Electrical conductivity (EC) values of the NaCl were settled 0 (distilled water), 4, 6, 8, 10 and 12 dS m-1. This investigation was performed as factorial arrangement of completely randomized design with four replications. Analysis of variance (ANOVA) showed that genotypes, salinity levels and interaction between genotype x salinity were significant for all the investigated treatments emergence index (EI), root dry weight (RDW), shoot dry weight (SDW), root length (RL), shoot length (SL), and salt tolerance indexes (STI). Results also revealed that the highest reduction in emergence index (59.7%) were obtained in the highest level (12 dS m-1) of salinity. The results further revealed that the cultivars named DKC 6589, PR31G98, and PR31A34 were the most tolerant genotypes than the others under NaCI stress.

Genomic, transcriptomic, and proteomic approaches towards understanding the molecular mechanisms of salt tolerance in Frankia strains isolated from Casuarina trees

BackgroundSoil salinization is a worldwide problem that is intensifying because of the effects of climate change. An effective method for the reclamation of salt-affected soils involves initiating plant succession using fast growing, nitrogen fixing actinorhizal trees such as the Casuarina. The salt tolerance of Casuarina is enhanced by the nitrogen-fixing symbiosis that they form with the actinobacterium Frankia. Identification and molecular characterization of salt-tolerant Casuarina species and associated Frankia is imperative for the successful utilization of Casuarina trees in saline soil reclamation efforts. In this study, salt-tolerant and salt-sensitive Casuarina associated Frankia strains were identified and comparative genomics, transcriptome profiling, and proteomics were employed to elucidate the molecular mechanisms of salt and osmotic stress tolerance.ResultsSalt-tolerant Frankia strains (CcI6 and Allo2) that could withstand up to 1000 mM NaCl and a salt-sensitive Frankia strain (CcI3) which could withstand only up to 475 mM NaCl were identified. The remaining isolates had intermediate levels of salt tolerance with MIC values ranging from 650 mM to 750 mM. Comparative genomic analysis showed that all of the Frankia isolates from Casuarina belonged to the same species (Frankia casuarinae). Pangenome analysis revealed a high abundance of singletons among all Casuarina isolates. The two salt-tolerant strains contained 153 shared single copy genes (most of which code for hypothetical proteins) that were not found in the salt-sensitive(CcI3) and moderately salt-tolerant (CeD) strains. RNA-seq analysis of one of the two salt-tolerant strains (Frankia sp. strain CcI6) revealed hundreds of genes differentially expressed under salt and/or osmotic stress. Among the 153 genes, 7 and 7 were responsive to salt and osmotic stress, respectively. Proteomic profiling confirmed the transcriptome results and identified 19 and 8 salt and/or osmotic stress-responsive proteins in the salt-tolerant (CcI6) and the salt-sensitive (CcI3) strains, respectively.ConclusionGenetic differences between salt-tolerant and salt-sensitive Frankia strains isolated from Casuarina were identified. Transcriptome and proteome profiling of a salt-tolerant strain was used to determine molecular differences correlated with differential salt-tolerance and several candidate genes were identified. Mechanisms involving transcriptional and translational regulation, cell envelop remodeling, and previously uncharacterized proteins appear to be important for salt tolerance. Physiological and mutational analyses will further shed light on the molecular mechanism of salt tolerance in Casuarina associated Frankia isolates.

Biochemical, physiological and molecular evaluation of rice cultivars differing in salt tolerance at the seedling stage.

Changes in the antioxidant enzymes, lipid peroxidation, sodium and potassium, chlorophyll, H2O2 and proline content were monitored in the leaves of 42 rice varieties which were not yet well-documented for the salinity tolerance under different salinity levels. The tolerant varieties (FL478, Hassani, Shahpasand, Gharib and Nemat) showed signs of tolerance (lower Na+/K+ ratio, high proline accumulation, less membrane damage, lower H2O2 production, and higher superoxide dismutase and catalase activity) very well. The positive relationship between the level of salt tolerance and the amount of proline accumulation in the rice varieties support the important role of proline under the salt stress. The varieties were genotyped for 12 microsatellite markers that were closely linked to SalTol QTL. The results of association analysis indicated that RM1287, RM8094, RM3412 and AP3206 markers had the high value of R2 for the regression models of the studied traits. It shows the important role of SalTol in controlling physio-biochemical traits. The results can be used in the future marker assisted selection (MAS) directly, if the results are confirmed.

Salicylic Acid Alleviates the Adverse Effects of Salt Stress on Dianthus superbus (Caryophyllaceae) by Activating Photosynthesis, Protecting Morphological Structure, and Enhancing the Antioxidant System.

Salt stress critically affects the physiological processes and morphological structure of plants, resulting in reduced plant growth. Salicylic acid (SA) is an important signal molecule that mitigates the adverse effects of salt stress on plants. Large pink Dianthus superbus L. (Caryophyllaceae) usually exhibit salt-tolerant traits under natural conditions. To further clarify the salt-tolerance level of D. superbus and the regulating mechanism of exogenous SA on the growth of D. superbus under different salt stresses, we conducted a pot experiment to examine the biomass, photosynthetic parameters, stomatal structure, chloroplast ultrastructure, reactive oxygen species (ROS) concentrations, and antioxidant activities of D. superbus young shoots under 0.3, 0.6, and 0.9% NaCl conditions, with and without 0.5 mM SA. D. superbus exhibited reduced growth rate, decreased net photosynthetic rate (Pn), increased relative electric conductivity (REC) and malondialdehyde (MDA) contents, and poorly developed stomata and chloroplasts under 0.6 and 0.9% salt stress. However, exogenously SA effectively improved the growth, photosynthesis, antioxidant enzyme activity, and stoma and chloroplast development of D. superbus. However, when the plants were grown under severe salt stress (0.9% NaCl condition), there was no significant difference in the plant growth and physiological responses between SA-treated and non-SA-treated plants. Therefore, our research suggests that exogenous SA can effectively counteract the adverse effect of moderate salt stress on D. superbus growth and development.

Seed pre-treatment with spermidine alleviates oxidative damages to different extent in the salt (NaCl)-stressed seedlings of three indica rice cultivars with contrasting level of salt tolerance

The effect of seed pre-treatment with the triamine, spermidine (Spd), in mitigating the detrimental effect of NaCl stress in rice is poorly explored. Due to limited available reports, such an investigation was carried out in the seedlings of three indica rice cultivars, IR-64 (salt-sensitive), Nonabokra (salt-tolerant) and Gobindobhog (aromatic and salt-sensitive). The lethal effect of NaCl was particularly noteworthy in the two susceptible cultivars IR-64 and Gobindobhog, as evidenced by extensive tissue-growth inhibition, oxidative damages and chlorophyll degeneration. Seed pre-treatment with Spd could remarkably alleviate stress injury, especially in IR-64 and Gobindobhog, by reverting back from growth retardation and oxidative damages to near-normal conditions. Spd pre-treatment also promoted the levels of osmolytes, particularly proline in Gobindobhog, concomitant with enhanced anthocyanin, cysteine and polyphenol oxidase, but lowered total phenolics and reducing power in the susceptible cultivars. However, the antioxidant enzyme activities were more enhanced in salt-stressed Nonabokra seedlings with Spd, as means of ameliorating cellular NaCl toxicity. A clear-cut variation in GPX, APX, CAT and SOD isozyme profile was discernible among the three cultivars during NaCl stress, with specific isoform(s) being up regulated or down regulated with Spd pre-treatment. Our results indicated that seed treatment with Spd at the pre-sowing stage can promote NaCl tolerance with varying degrees in salt-sensitive and salt-tolerant rice cultivars by alleviating oxidative damages, triggering the antioxidants and osmolytes, and activating the antioxidative enzymes.

Exogenous Glutathione Modulates Salinity Tolerance of Soybean [Glycine max (L.) Merrill] at Reproductive Stage

In this study, we evaluated salt stress responses of 11 soybean genotypes and explored the protective roles of exogenous glutathione (GSH) against salt toxicity by assessing various biochemical and yield-attributing parameters. Exposure of the soybean genotypes to salt stress at the reproductive (R1) stage significantly decreased their yields by down-regulating the yield-contributing parameters as compared with unstressed controls. The highest decrease was found in number of seeds plant−1, yield plant−1, and number of pods plant−1, whereas the lowest decrease was recorded in number of seeds pod−1. Exogenous GSH was found to be effective in improving salinity tolerance, and the highest positive effects of GSH were recorded in terms of yield plant−1, number of seeds plant−1 and number of pods plant−1, whereas its lowest effect was observed with respect to the 100-seed weight. Cluster analysis of the genotypes based on yield-contributing and yield data revealed different levels of salt tolerance. Notably, BINA-01 and -02, and BINA-04 were recognized as the highest and lowest salt-tolerant genotypes, respectively. Furthermore, exogenous GSH alleviated oxidative stress in the representative contrasting genotypes at the vegetative (V3) stage by decreasing salt-induced accumulation of malondialdehyde and hydrogen peroxide. Taken together, our findings revealed that exogenous GSH application can minimize oxidative stress and contribute to the improvement of yield-contributing parameters, leading to improved yield in soybean genotypes under salt stress. Further investigations on molecular aspects will enable us to gain an in-depth understanding of how exogenous GSH can improve salinity tolerance in soybean, particularly at reproductive stage, to discover relevant pathways for biotechnological manipulation.

Induction of salt tolerance in salicylate-deficient NahG Arabidopsis transformants using the nitric oxide donor

The effects of treatment with nitric oxide donor sodium nitroprusside (SNP, 0.5 mM) on salt tolerance of wild type (Col–0) Arabidopsis thaliana plants and Arabidopsis thaliana plants transformed with the bacterial salicylate hydroxylase gene (NahG) were compared. Basic salt tolerance level (200 mM NaCl) was higher in NahG transformants. Under salt stress conditions, these plants showed higher activity levels for antioxidant enzymes as well as higher content of sugars and anthocyanins. The treatment with NO donor induced salt tolerance in the plants of both genotypes, which could be observed as less strong growth inhibition, reduced oxidative damage, and preservation of chlorophyll pool in leaves. After the exposure to salt stress, the activity of both superoxide dismutase and guaiacol peroxidase was higher in SNP-treated wild type plants and NahG transformants than in the nontreated plants. After the imposition of salt stress, proline content in leaves of the wild type plants treated with the nitric oxide donor was lower than in the leaves of the nontreated plants. In contrast, SNP treatment of NahG transformants led to a significant increase in the proline content in leaves under the salt stress conditions. Conclusions have been made that wild type Col-0 plants and NahG transformants differ in how their systems of protection against salt stress are activated and that nitric oxideinduced mobilization of protection systems in A. thaliana may not require the presence of salicylate.

Salt and heavy metal tolerance and expression levels of candidate tolerance genes among four extremophile Cochlearia species with contrasting habitat preferences.

To test the concept of a general "mineral stress tolerance", we compared four extremophile Cochlearia species for salt (NaCl), zinc (Zn) and cadmium (Cd) tolerance and accumulation, and for expression of candidate tolerance genes for salt and Zn tolerance. Salt tolerance decreased in the order C. anglica>C. x hollandica>C. danica>C. pyrenaica, corresponding with the average salinity levels in the species' natural environments. The glycophytic metallophyte, C. pyrenaica, showed a relatively high level of salt tolerance, compared to other glycophytic Brassicaceae. Salt tolerance was positively correlated with HKT1 expression and the K+ concentration in roots under salt exposure, but uncorrelated with the Na+ concentrations in roots and shoots. All the species accumulated Na+ primarily in their leaves, and exhibited a high NHX1 expression in leaves, in comparison with other glycophytic Brassicaceae, suggesting that salt tolerance in Cochlearia is based on an efficient vacuolar sequestration of Na+ in leaves. The metallicolous C. pyrenaica population was hypertolerant to Zn, but not to Cd, in comparison with the other Cochlearia species. All the Cochlearia species accumulated Zn and Cd primarily in roots, and showed high levels of Cd and Zn tolerance, with unusually low rates of metal accumulation, in comparison with non-metallophytes, or non-metallicolous metallophyte populations, of species belonging to other genera or families. Although Cochlearia, as a genus, shows relatively high levels of tolerance to both salt and heavy metals, this is most probably not due to a common 'mineral stress tolerance' mechanism.

In-vitro Mutagenesis Induction to Improve Abiotic Stress in Tissue Cultured Plantlet of Picrohiza kurroa Royle ex. Benth: An Endangered Plant of Western Himalayas, India

The study is focused to establish an improved salt and drought tolerant Picrohiza kurroa Royle ex Benth, an endangered medicinal plant of Western Himalayas through mutagenesis system in conjunction with in- vitro regeneration technique. Regeneration using leaf as explants from mature plant of characterized germplasm is beneficial because the source plant is not damaged. Efficient callus formation i.e., 85% was achieved in modified MS medium at 2,4-D at 3.5 mg L-1. Ethyl methane sulfonate (EMS) a chemical mutagen was used to induce mutation in the callus biomass under in-vitro condition. Relatively decreases in callus biomass were observed as the dose of mutagenic chemical increased from 0.0 to 0.8 mM. Selection of mutants callus lines were also investigated against salt (NaCl) and drought (mannitol) tolerance level by using its various concentrations i.e., 50 to 250 mM L-1. In mutagenized callus (MC) under both stress responses there was increase in callus biomass with the successive increase in concentration of NaCl and Mannitol till 100 mM L-1, after that it started decline. Stress tolerated mutant callus line were also characterized by the accumulation of proline and glycine betaine (GB) content. At 100 mM L-1 concentrations of NaCl and mannitol, higher proline and GB content were accumulated in the mutagenized callus i.e., 5.23 and 5.18 µmol g-1 FW and 11.23 and 11.98 µg g-1 FW respectively which is significantly higher in comparison to non-mutagenized callus (UM). For shoot proliferation in mutant callus line, various concentrations with combination of plant growth regulators (PGR’s) were used in treatments (T1, T2 and T3). Invariably, in treatment T3 the concentration of 1.0+0.5 mg L-1 resulted in highest shoot regeneration i.e., 85% while minimum 20% was obtained in T1 at concentration 0.5+0.1 mg L-1. NAA fortified MS medium was found superior to IAA and IBA with respect to the induction of roots. The mutant and stress selected grown through tissue engineering were evaluated for their ex situ agronomic performance in saline as well as drought condition for 30 days. Under both stress condition the mutant plant revealed a remarkable increase in all the parameters studied i.e., shoot and root length, fresh and dry root, shoot biomass and number of leaves with respect to normal plant (control).

Seed priming with spermine ameliorates salinity stress in the germinated seedlings of two rice cultivars differing in their level of salt tolerance

Seed priming with spermine ameliorates salinity stress in the germinated seedlings of two rice cultivars differing in their level of salt tolerance

A Non-specific Setaria italica Lipid Transfer Protein Gene Plays a Critical Role under Abiotic Stress.

Lipid transfer proteins (LTPs) are a class of cysteine-rich soluble proteins having small molecular weights. LTPs participate in flower and seed development, cuticular wax deposition, also play important roles in pathogen and abiotic stress responses. A non-specific LTP gene (SiLTP) was isolated from a foxtail millet (Setaria italica) suppression subtractive hybridization library enriched for differentially expressed genes after abiotic stress treatments. A semi-quantitative reverse transcriptase PCR analysis showed that SiLTP was expressed in all foxtail millet tissues. Additionally, the SiLTP promoter drove GUS expression in root tips, stems, leaves, flowers, and siliques of transgenic Arabidopsis. Quantitative real-time PCR indicated that the SiLTP expression was induced by NaCl, polyethylene glycol, and abscisic acid (ABA). SiLTP was localized in the cytoplasm of tobacco leaf epidermal cells and maize protoplasts. The ectopic expression of SiLTP in tobacco resulted in higher levels of salt and drought tolerance than in the wild type (WT). To further assess the function of SiLTP, SiLTP overexpression (OE) and RNA interference (RNAi)-based transgenic foxtail millet were obtained. SiLTP-OE lines performed better under salt and drought stresses compared with WT plants. In contrast, the RNAi lines were much more sensitive to salt and drought compared than WT. Electrophoretic mobility shift assays and yeast one-hybrids indicated that the transcription factor ABA-responsive DRE-binding protein (SiARDP) could bind to the dehydration-responsive element of SiLTP promoter in vitro and in vivo, respectively. Moreover, the SiLTP expression levels were higher in SiARDP-OE plants compared than the WT. These results confirmed that SiLTP plays important roles in improving salt and drought stress tolerance of foxtail millet, and may partly be upregulated by SiARDP. SiLTP may provide an effective genetic resource for molecular breeding in crops to enhance salt and drought tolerance levels.

Plant growth promotion properties of bacterial strains isolated from the rhizosphere of the Jerusalem artichoke (Helianthus tuberosus L.) adapted to saline-alkaline soils and their effect on wheat growth.

The Jerusalem artichoke (JA; Helianthus tuberosus), known to be tolerant to saline-alkaline soil conditions, has been cultivated for many years in the Yellow River delta, Shandong Province coastal zone, in China. The aim of our study was to isolate nitrogen-fixing bacteria colonizing the rhizosphere of JA and to characterize other plant growth promotion properties. The ultimate goal was to identify isolates that could be used as inoculants benefiting an economic crop, in particular for improving wheat growth production in the Yellow River delta. Bacterial strains were isolated from the rhizosphere soil of JA on the basis of growth on nitrogen-free Ashby medium. Identification and phylogenetic analysis was performed after nucleotide sequencing of 16S rRNA gene. Plant-growth-promoting traits, such as nitrogen fixation activity, phosphate solubilization activity, indole-3-acetic acid production, were determined using conventional methods. Eleven strains were isolated and 6 of them were further examined for their level of salt tolerance and their effect on plant growth promotion. Inoculation of Enterobacter sp. strain N10 on JA and wheat led to significant increases in both root and shoot dry mass and shoot height. Enterobacter sp. strain N10 appeared to be the best plant-growth-promoting rhizobacteria to increase wheat productivity in future field applications.

Occurrence of islands in genomes of Sinorhizobium meliloti native isolates

Genomes of 184 Sinorhizobium meliloti native isolates were studied to test the occurence of islands Sme21T, Sme19T, and Sme80S previously described in the model strain Rm1021. This analysis was conducted using PCR methodology involving specific primers. It was demonstrated that, in the examined geographically distinct populations of S. meliloti from the Northern Caucasus (NCG) and the Aral Sea region (PAG), the strains containing genomic islands were observed with similar frequency (0.55 and 0.57, respectively). Island Sme80S, denoted as an island of “environmental adaptivity,” was identified predominantly (frequency of 0.38) in genomes of strains which exhibited a lower level of salt tolerance and was isolated in PAG, a modern center of introgressive hybridization of alfalfa subjected to salinity. Island Sme21T designated as “ancestral” was observed in genomes of strains isolated in NCG, the primary center of host-plant biodiversity, 10-fold more often than in strains from PAG. An island Sme19T, which predominantly carries genes encoding transposases, was observed in genomes of strains in both populations with average frequency of 0.10. The analysis of linkage disequilibrium (LD) based on the assessment of probability for detection of different islands combinations in genomes revealed an independent inheritance of islands in salt-sensitive strains of various geographic origin. In contrast, the absence of this trend was noted in the majority of the examined combinations of salt-tolerant strains. It was concluded that the structure of chromosome in PAG strains which predominantly possessed a salt-sensitive phenotype was subjected to active recombinant processes, which could predetermine the intensity of microevolutionary processes in bacterial populations and facilitate an adaptation of bacteria in adverse environmental effect.

Retrotransposon insertion variations in doubled haploid bread wheat mutants

The current study attempted to obtain candidate doubled haploid (DH) wheat lines by serially combining two approaches: conventional chemical mutagenesis and anther culture. Additionally, the salt tolerance levels were examined between stress-treated (100 mM NaCl) and non-treated DH groups. For the molecular analysis, IRAP markers were used to characterize retrotransposon insertion polymorphisms induced by haploidization, chromosome doubling, and/or mutagenesis in the DH lines. Various sodium azide (NaN3) concentrations (from 0 to 5 mM) were applied to seeds of the Pehlivan wheat cultivar to obtain an M1 generation mutant population. Anther culture was set up from the M1 mutant population. Green plant regeneration, the frequency of selected candidate mutants within the DH form and the levels of salt tolerance between samples were screened. A total of eight thousand anthers were cultured, and sixteen candidate salt-tolerant DH mutant lines, twenty-seven candidate DH mutant lines with different characteristics and one hundred and two candidate DH lines with morphologically normal appearances were obtained from the NaN3-mutagenized population. The IRAP patterns were quite similar between the control DH lines, and the genetic differences between the controls and DHs originating from possible mutants showed close relatedness. According to previous studies, chemical mutagenesis and anther culture were combined for the first time to detect candidate salt tolerant genotypes at the DH stage. This approach might also be useful for determining the threshold dose and efficiency of wheat mutagens.

Utilization of sea water based media for the production and characterization of cellulase by Fusarium subglutinans MTCC 11891

Abstract The present study focuses on isolation, screening and identification of fungal strain capable of producing cellulase enzyme in sea water based media from paddy fields of Rourkela, Odisha, India. The filamentous fungi isolated were identified as Fusarium subglutinans MTCC 11891. Cellulase enzyme was characterized for its optimal pH and temperature and also studied for the effect of metal ions on enzyme activity. Comparative studies were carried out using both fresh and sea water based media in order to investigate the salt tolerance level of cellulase produced by the fungal strain. The fungal strain was found to be halotolerant with optimal pH of 5.0 with cellulase activity of 292.53 U/mL and 184 U/mL in fresh and sea water based Mandel's media, respectively. The optimal temperature for F. subglutinans MTCC 11891 cellulase was recorded at 80 °C with 347.43 U/mL for fresh water and 232 U/mL for sea water based Mandel's media. Manifold increase in cellulase activity was evidenced in the presence of 5 mM Mn 2+ and Fe 2+ concentration in both fresh and sea water based Mandel's media suggesting these two cations as key catalytic molecules. Partial purification of the cellulase produced in fresh water based Mandel's media was performed using diethylaminoethanol (DEAE)-Sepharose column and the fraction with enzyme activity of 298.68 U/mL was recorded as fraction with highest cellulase concentration. Halotolerant cellulases would be more useful in future for the development of sea water based systems to produce bioethanol.

Permanent Draft Genome Sequence of Frankia sp . Strain Allo2, a Salt-Tolerant Nitrogen-Fixing Actinobacterium Isolated from the Root Nodules of Allocasuarina

Frankia sp. strain Allo2 is a member of Frankia lineage Ib, which is able to reinfect plants of the Casuarinaceae family, and exhibits a high level of salt tolerance compared to other isolates. Here, we report the 5.3-Mbp draft genome sequence of Frankia sp. strain Allo2 with a G+C content of 70.0% and 4,224 candidate protein-encoding genes.

Suppression of PCD-related genes affects salt tolerance in Arabidopsis

This work aims at examining a natural exciting phenomenon suggesting that suppression of genes inducing programmed cell death (PCD) might confer tolerance against abiotic stresses in plants. PCD-related genes were induced in tobacco under oxalic acid (OA) treatment (20mM), and plant cells were characterized to confirm the incidence of PCD. The results indicated that PCD was triggered 24h after the exposure to OA. Then, RNAs were extracted from tobacco cells 0, 2, 6, 12 and 24h after treatment for deep sequencing. RNA-Seq analyses were done with a special emphasis to clusters whose PCD-related genes were upregulated after 2h of OA exposure. Accordingly, 23 tobacco PCD-related genes were knocked down via virus-induced gene silencing (VIGS), whereas our results indicated the influence of five of them on inducing or suppressing PCD. Knockout T-DNA insertion mutants of these five genes in Arabidopsis were tested under salt stress (0, 100, 150, and 200mM NaCl), and the results indicated that a mutant of an antiapoptotic gene, namely Bax Inhibitor-1 (BI-1), whose VIGS induced PCD in tobacco, was salt sensitive, while a mutant of an apoptotic gene, namely mildew resistance locus O (Mlo), whose VIGS suppressed PCD, was salt tolerant as compared to the WT (Col) control. These data support our hypothesis that retarding PCD-inducing genes can result in higher levels of salt tolerance, while retarding PCD-suppressing genes can result in lower levels of salt tolerance in plants.