Salinity Tolerance Genes Research Articles

QTLs for stomatal and photosynthetic traits related to salinity tolerance in barley

BackgroundStomata regulate photosynthesis and transpiration, and these processes are critical for plant responses to abiotic stresses such as salinity. A barley double haploid population with 108 lines derived from a cross between CM72 (salt-tolerant) and Gairdner (salt-sensitive) was used to detect quantitative trait loci (QTLs) associated with stomatal and photosynthetic traits related to salinity tolerance.ResultsA total of 11 significant QTLs (LOD > 3.0) and 11 tentative QTLs (2.5 < LOD < 3.0) were identified. These QTLs are distributed on all the seven chromosomes, except 5H and explain 9.5–17.3% of the phenotypic variation. QTLs for biomass, intercellular CO2 concentration, transpiration rate and stomatal conductance under control conditions co-localised together. A QTL for biomass also co-located with one for transpiration rate under salinity stress. A linkage was found between stomatal pore area and gas exchange. A QTL for salinity tolerance also co-localised with QTLs for grain yield and biomass on chromosome 3H. Based on the draft barley genome, the candidate genes for salinity tolerance at this locus are proposed.ConclusionsThe lack of major QTLs for gas exchange and stomatal traits under control and saline conditions indicates a complex relationship between salinity and leaf gas exchange due to the fact that these complex quantitative traits are under the control of multiple genes.

The expression of GmP5CS, GmPAP3, and GmBZIP50 genes under saline condition in soybean using real-time PCR

Salinity in higher plants is the cause of toxicity and osmotic stress. To identify the expression pattern of salinity tolerance genes in soybean, it was investigated the relative expression of three genes, GmPAP3, GmBZIP50 and GmP5CS at two tissues leaf and root in Williams (as tolerant) and L17 (as susceptible) soybean genotypes under two levels zero (control) and 300 Mm NaCl. For adaptation of plantlets to salinity, salinity was started with 150 mM NaCl for first time and followed by 300 mM NaCl in two times. The housekeeping gene 18SrRNA was used to normalize data. Data analysis showed that all three genes expression increased under salinity stress. The expression of GmP5CS and GmBZIP50 was two-fold greater in Williams than in L17 genotype, while GmPAP3 expression was 2.5-fold greater in L17 than in Williams. The expression of GmP5CS and GmBZIP50 was higher in roots than in leaves, while GmPAP3 expression was higher in leaves than in roots. In conclusion, GmBZIP50 over-expressed more than two other genes by 375 and 273% in leaves and roots under stressed compared to non-stressed plants. Thus GmBZIP50 could be more effective candidate gene for producing soybeans with resistance to salinity that may be resulted from transferring and increasing copy number.

A novel phytoene synthase paralog from halophytic Salicorniaconfers salinity tolerance in plants

Salicornia seems to be a suitable euhalophyte for the study of salt stress resilience mechanism and exploitation of salinity-tolerant genes for crop yield improvement. In this study, we cloned a novel SePSY1 gene from an extremely salt-tolerant glycophyte, Salicornia europaea. The sequence analysis revealed that the newly isolated gene is a paralog of PSY, suggesting a gene duplication event in Salicornia. The newly isolated gene encodes a protein of 419 amino acids. The C-terminus containing a Trans-IPPS-H domain with catalytic and binding regions exhibits considerable conservation in various species, while the N-terminus remained divergent. The structural analysis suggested a catalytic role of the C-terminus in the first step of carotenoid biosynthesis, whereas N-terminus is involved in the transport and localization of protein. Gene expression using real-time RT-PCR revealed enhanced transcript signals for salt-treated plants. Transgenic Arabidopsis plants overexpressing SePSY1 could withstand 200 mM salt stress in comparison with the wild-type counterpart. Thus, SePSY1 confers salinity stress tolerance in the heterologous system. Strength of gene expression is positively correlated with severity of phenotypes. Our results reveal that the SePSY1 gene can be a potential target for improving salinity tolerance in crop plants that are susceptible to this stress.

Molecular Dissection of Seedling Salinity Tolerance in Rice (Oryza sativa L.) Using a High-Density GBS-Based SNP Linkage Map.

BackgroundSalinity is one of the many abiotic stresses limiting rice production worldwide. Several studies were conducted to identify quantitative trait loci (QTLs) for traits associated to salinity tolerance. However, due to large confidence interval for the position of QTLs, utility of reported QTLs and the associated markers has been limited in rice breeding programs. The main objective of this study is to construct a high-density rice genetic map for identification QTLs and candidate genes for salinity tolerance at seedling stage.ResultsWe evaluated a population of 187 recombinant inbred lines (RILs) developed from a cross between Bengal and Pokkali for nine traits related to salinity tolerance. A total of 9303 SNP markers generated by genotyping-by-sequencing (GBS) were mapped to 2817 recombination points. The genetic map had a total map length of 1650 cM with an average resolution of 0.59 cM between markers. For nine traits, a total of 85 additive QTLs were identified, of which, 16 were large-effect QTLs and the rest were small-effect QTLs. The average interval size of QTL was about 132 kilo base pairs (Kb). Eleven of the 85 additive QTLs validated 14 reported QTLs for shoot potassium concentration, sodium-potassium ratio, salt injury score, plant height, and shoot dry weight. Epistatic QTL mapping identified several pairs of QTLs that significantly contributed to the variation of traits. The QTL for high shoot K+ concentration was mapped near the qSKC1 region. However, candidate genes within the QTL interval were a CC-NBS-LRR protein, three uncharacterized genes, and transposable elements. Additionally, many QTLs flanked small chromosomal intervals containing few candidate genes. Annotation of the genes located within QTL intervals indicated that ion transporters, osmotic regulators, transcription factors, and protein kinases may play essential role in various salt tolerance mechanisms.ConclusionThe saturation of SNP markers in our linkage map increased the resolution of QTL mapping. Our study offers new insights on salinity tolerance and presents useful candidate genes that will help in marker-assisted gene pyramiding to develop salt tolerant rice varieties.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0125-2) contains supplementary material, which is available to authorized users.

Comparative transcriptomic profiling of larvae and post-larvae of Macrobrachium rosenbergii in response to metamorphosis and salinity exposure

The high-throughput sequencing technology provides a platform for revealing the expressed genes within a tissue at a specific time. The giant freshwater prawn, Macrobrachium rosenbergii, is an economically important species, which is surviving in a wide-range of salinity. In this study, to understand the physiological mechanism of adaptability with respect to moulting and salinity; transcriptome sequencing of larvae and post-larvae of M. rosenbergii was performed using the Illumina GAIIx platform. The generated raw read-data comprised 71,391,946 and 75,276,622 paired-end reads (PE) for larvae and post-larvae respectively. Using CLC bio Genomic Workbench version 7.5 (CGWB), 71.39 million and 75.27 million of each 72 base paired-end, high quality reads were assembled into 43,383 (N50 1852) and 44,960 (N50 1874) transcripts, respectively, for larvae and post-larvae. The nucleotide level annotation of both transcriptomes showed significant similarity with unigenes of closely related species. The Gene Ontology analysis suggested enrichment of transcripts involving several biological processes linked to transcriptional regulation, signal transduction, immune response, ion-binding. Differential gene expression analysis using CGWB and DESeq identified 9680 deregulated genes of which 3454 unigenes were up-regulated and 3068 down-regulated by ≥1.5 fold (p < 0.05) in larval stage compared to post-larval stage. However, in larval stage 938 genes were down regulated and 1599 genes up-regulated by ≥3 fold with p < 0.05. GO enrichment of differentially expressed genes was shown several molecular functions for maintaining homeostasis against salinity stress. To validate the expression patterns, few transcripts were chosen for quantitative real-time PCR that showed the consistency and exactness of our analysis. In addition, we also speculated the enzymatic pathway using KEGG, which depicted that up-regulated genes are involved in several significant metabolic pathways and those are critical for maintaining osmoregulation and linked with metamorphosis. Therefore, we have generated valuable information of salinity tolerant genes in the larval and post larval stage of M. rosenbergii during salt- and freshwater compliances, which will be further harnessed for gene targeting. The present finding would provide the basis for further screening of salt tolerant genes associated markers for selective breeding.

Functional Identification and Characterization of Genes Cloned from Halophyte Seashore Paspalum Conferring Salinity and Cadmium Tolerance.

Salinity-affected and heavy metal-contaminated soils limit the growth of glycophytic plants. Identifying genes responsible for superior tolerance to salinity and heavy metals in halophytes has great potential for use in developing salinity- and Cd-tolerant glycophytes. The objective of this study was to identify salinity- and Cd-tolerance related genes in seashore paspalum (Paspalum vaginatum), a halophytic perennial grass species, using yeast cDNA expression library screening method. Based on the Gateway-compatible vector system, a high-quality entry library was constructed, which contained 9.9 × 106 clones with an average inserted fragment length of 1.48 kb representing a 100% full-length rate. The yeast expression libraries were screened in a salinity-sensitive and a Cd-sensitive yeast mutant. The screening yielded 32 salinity-tolerant clones harboring 18 salinity-tolerance genes and 20 Cd-tolerant clones, including five Cd-tolerance genes. qPCR analysis confirmed that most of the 18 salinity-tolerance and five Cd-tolerance genes were up-regulated at the transcript level in response to salinity or Cd stress in seashore paspalum. Functional analysis indicated that salinity-tolerance genes from seashore paspalum could be involved mainly in photosynthetic metabolism, antioxidant systems, protein modification, iron transport, vesicle traffic, and phospholipid biosynthesis. Cd-tolerance genes could be associated with regulating pathways that are involved in phytochelatin synthesis, HSFA4-related stress protection, CYP450 complex, and sugar metabolism. The 18 salinity-tolerance genes and five Cd-tolerance genes could be potentially used as candidate genes for genetic modification of glycophytic grass species to improve salinity and Cd tolerance and for further analysis of molecular mechanisms regulating salinity and Cd tolerance.

Joint genetic and network analyses identify loci associated with root growth under NaCl stress in Arabidopsis thaliana.

Plants have evolved a series of tolerance mechanisms to saline stress, which perturbs physiological processes throughout the plant. To identify genetic mechanisms associated with salinity tolerance, we performed linkage analysis and genome-wide association study (GWAS) on maintenance of root growth of Arabidopsis thaliana in hydroponic culture with weak and severe NaCl toxicity. The top 200 single-nucleotide polymorphisms (SNPs) determined by GWAS could cumulatively explain approximately 70% of the variation observed at each stress level. The most significant SNPs were linked to the genes of ATP-binding cassette B10 and vacuolar proton ATPase A2. Several known salinity tolerance genes such as potassium channel KAT1 and calcium sensor SOS3 were also linked to SNPs in the top 200. In parallel, we constructed a gene co-expression network to independently verify that particular groups of genes work together to a common purpose. We identify molecular mechanisms to confer salt tolerance from both predictable and novel physiological sources and validate the utility of combined genetic and network analysis. Additionally, our study indicates that the genetic architecture of salt tolerance is responsive to the severity of stress. These gene datasets are a significant information resource for a following exploration of gene function.

Proteome Analysis of Date Palm (Phoenix dactylifera L.) under Severe Drought and Salt Stress.

Date palm cultivars differently tolerate salinity and drought stress. This study was carried out to study the response of date palm to severe salinity and drought based on leaf proteome analysis. Eighteen-month-old date palm plants were subjected to severe salt (48 g/L NaCl) and drought (82.5 g/L PEG or no irrigation) conditions for one month. Using a protein 2D electrophoresis method, 55 protein spots were analyzed using mass spectrometry. ATP synthase CF1 alpha chains were significantly upregulated under all three stress conditions. Changes in the abundance of RubisCO activase and one of the RubisCO fragments were significant in the same spots only for salt stress and drought stress with no irrigation, and oxygen-evolving enhancer protein 2 was changed in different spots. Transketolase was significantly changed only in drought stress with PEG. The expression of salt and drought stress genes of the chosen protein spots was either overexpressed or downexpressed as revealed by the high or low protein abundance, respectively. In addition, all drought tolerance genes due to no irrigation were downregulated. In conclusion, the proteome analysis of date palm under salinity and drought conditions indicated that both salinity and drought tolerance genes were differentially expressed resulting in high or low protein abundance of the chosen protein spots as a result of exposure to drought and salinity stress condition.

Evaluation of potential candidate genes involved in salinity tolerance in striped catfish (Pangasianodon hypophthalmus) using an RNA-Seq approach

Increasing salinity levels in freshwater and coastal environments caused by sea level rise linked to climate change is now recognized to be a major factor that can impact fish growth negatively, especially for freshwater teleost species. Striped catfish (Pangasianodon hypophthalmus) is an important freshwater teleost that is now widely farmed across the Mekong River Delta in Vietnam. Understanding the basis for tolerance and adaptation to raised environmental salinity conditions can assist the regional culture industry to mitigate predicted impacts of climate change across this region.Attempt of next generation sequencing using the ion proton platform results in more than 174 million raw reads from three tissue libraries (gill, kidney and intestine). Reads were filtered and de novo assembled using a variety of assemblers and then clustered together to generate a combined reference transcriptome. Downstream analysis resulted in a final reference transcriptome that contained 60,585 transcripts with an N50 of 683bp. This resource was further annotated using a variety of bioinformatics databases, followed by differential gene expression analysis that resulted in 3062 transcripts that were differentially expressed in catfish samples raised under two experimental conditions (0 and 15ppt). A number of transcripts with a potential role in salinity tolerance were then classified into six different functional gene categories based on their gene ontology assignments. These included; energy metabolism, ion transportation, detoxification, signal transduction, structural organization and detoxification.Finally, we combined the data on functional salinity tolerance genes into a hypothetical schematic model that attempted to describe potential relationships and interactions among target genes to explain the molecular pathways that control adaptive salinity responses in P. hypophthalmus. Our results indicate that P. hypophthalmus exhibit predictable plastic regulatory responses to elevated salinity by means of characteristic gene expression patterns, providing numerous candidate genes for future investigations.

Co-expression of xerophyte Zygophyllum xanthoxylum ZxNHX and ZxVP1-1 confers enhanced salinity tolerance in chimeric sugar beet (Beta vulgaris L.).

Salinity is one of the major abiotic stresses that limit the growth and productivity of sugar beet (Beta vulgaris L.). To improve sugar beet’s salinity tolerance, the ZxNHX and ZxVP1-1 genes encoding tonoplast Na+/H+ antiporter and H+-PPase from xerophyte Zygophyllum xanthoxylum were co-expressed by Agrobacterium tumefaciens-mediated transformation. It is showed here that co-expression of ZxNHX and ZxVP1-1 confers enhanced salinity tolerance to the transformed sugar beet plants compared with the wild-type (WT) plants. The chimeric plants grew well in the presence of high salinity (400 mM NaCl), whereas WT plants displayed chlorosis and died within 8 days. Compared to WT plants, the chimeric plants co-expressing ZxNHX and ZxVP1-1 accumulated more proline, Na+ and K+ in their leaves and petioles when exposed to high salinity, which caused lower solute potential, retained more water and thus subjected to lesser cell membrane damage. Interestingly, the chimeric plants accumulated higher sucrose, glucose and fructose contents in their storage roots than WT plants in the absence or presence of high salinity. Our results suggested that co-expression of ZxNHX and ZxVP1-1 improved the osmoregulatory capacity in chimeric sugar beet through increased compartmentalization of ions into the vacuoles by enhancing the activity of proton pumps and thus mitigated Na+-toxicity for plants.

Isolation of genes conferring salt tolerance from Piriformospora indica by random overexpression in Escherichia coli.

Piriformospora indica, a root endophytic fungus identified in the Indian Thar desert, colonizes the roots of plants and provides resistance towards biotic stress as well as tolerance to abiotic stress in the plants. Despite its positive impact on the host, little is known about the P. indica genes that are involved in salt stress tolerance. Therefore this study was conducted to identify and isolate high salinity-tolerance genes from P. indica. Thirty-six salinity-tolerance genes were obtained by functional screening, based on random over expression of a P. indica cDNA library in Escherichia coli grown on medium supplemented with 0.6 M NaCl. The salinity tolerance conferred by these 36 genes in bacteria was further confirmed by using another strain of E. coli (DH5α) transformants. However when the expression of these 36 genes was analysed in P. indica using quantitative RT-PCR, we found only six genes were up-regulated by salt stress. These six genes are involved in different cellular processes, such as metabolism, energy and biosynthetic processes, DNA repair, regulation of protein turnover, transport and salt stress tolerance. This work presents the basis for further molecular analyses of the mechanisms of salt tolerance in P. indica and for the use of this endophyte to confer salt tolerance to plants.

Functional Analysis of Two Orthologous NAC Genes, CarNAC3, and CarNAC6 from Cicer arietinum, Involved in Abiotic Stresses in Poplar

Abiotic stresses such as drought and high salinity inhibit plant growth and productivity. NAC transcription factors play a variety of important roles in plant development and abiotic stress responses. To date, the transformation of NAC genes into poplar plants has not been reported. In this study, we introduced the CarNAC3 and CarNAC6 salinity and drought tolerant genes from Cicer arietinum (chickpea) into Populus deltoides × Populus euramericana ‘Nanlin895’ (poplar) plants using Agrobacterium tumefaciens-mediated transformation. We verified the integration of the two genes into the poplar genome using polymerase chain reaction (PCR) and their stable expression was confirmed at the transcript level using real-time (RT)-PCR. The growth rates of roots and shoots and the clawed root rate increased in transformed plants grown in agar medium or in soil and increased in response to drought and salt stress conditions. Proline and photoprotectant pigment accumulation and antioxidant enzyme activities increased in response to abiotic stress, but the accumulation of photosynthetic pigments and malondialdehyde (MDA) decreased in transgenic lines relative to wild-type control plants. The CarNAC3 transgene was expressed at higher levels than the CarNAC6 transgene. Our results showed that the CarNAC3 and CarNAC6 genes enhanced the capacity for osmotic adjustment and increased antioxidant enzyme activity and suggest that these genes could play a significant role in improving drought and salt tolerance when expressed in poplar plants.

&lt;b&gt; Detection of genes providing salinity-tolerance in rice&lt;/b&gt; - doi: 10.4025/actascibiolsci.v36i1.15437

The present study aimed to identify salinity-tolerant genes in three cultivars (BRS-7 Taim, BRS Querência and BRS Atalanta) of Oryza sativa L. ssp. indica S. Kato and in three cultivars (BRS Bojurú, IAS 12-9 Formosa and Goyakuman) of Oryza sativa L. ssp. japonica S. Kato. Ten days after emergence seedlings were transferred to a greenhouse and placed in a 15L vessel with half strength Hoagland nutrient solution, which was changed every four days, under controlled temperature and humidity. Plants were harvested 56 days after transfer. DNA extraction was carried out by CTAB method and salinity-tolerant genes SOS and CK1 were identified by in silico research. Amplification of gene sequence was performed with in silico primers. Bands were detected by agar gel electrophoresis and visualized under ultraviolet light after staining with ethidium bromide. Gene SOS1 fragments were present in all cultivars, except in BRS Atalanta, whereas CK1 gene was present in all evaluated cultivars. Results show that salinity-tolerant genes under analysis were identified in the two sub-species.

Mapping quantitative trait loci associated with yield and yield components under reproductive stage salinity stress in rice (Oryza sativa L.)

Salinity tolerance in rice is critical at reproductive stage because it ultimately determines grain yield. An F2 mapping population derived from a Sadri/FL478 cross was exposed to saline field conditions (6-8 dS m(-1)) after the active tillering stage to identify reproductive stage specific QTLs for salinity tolerance. Genetic linkage map was constructed using 123 microsatellite markers on 232 F2 progenies. Totally 35 QTLs for 11 traits under salinity stress were detected with LOD > 3, out of which 28 QTLs that explained from 5.9 to 30.0% phenotypic variation were found to be significant based on permutation test. Three major QTL clusters were found on chromosomes 2 (RM423-RM174), 4 (RM551-RM518) and 6 (RM20224-RM528) for multiple traits under salinity stress. Both parental lines contributed additively for QTLs identified for the yield components. A majority of the QTLs detected in our study are reported for the first time for reproductive stage salinity stress. Fine-mapping of selected putative QTLs will be the next step to facilitate marker-assisted backcrossing and to detect useful genes for salinity tolerance at the reproductive stage in rice.

Genomewide discovery ofDNApolymorphisms in rice cultivars with contrasting drought and salinity stress response and their functional relevance

Next-generation sequencing technologies provide opportunities to understand the genetic basis of phenotypic differences, such as abiotic stress response, even in the closely related cultivars via identification of large number of DNA polymorphisms. We performed whole-genome resequencing of three rice cultivars with contrasting responses to drought and salinity stress (sensitive IR64, drought-tolerant Nagina 22 and salinity-tolerant Pokkali). More than 356 million 90-bp paired-end reads were generated, which provided about 85% coverage of the rice genome. Applying stringent parameters, we identified a total of 1 784 583 nonredundant single-nucleotide polymorphisms (SNPs) and 154 275 InDels between reference (Nipponbare) and the three resequenced cultivars. We detected 401 683 and 662 509 SNPs between IR64 and Pokkali, and IR64 and N22 cultivars, respectively. The distribution of DNA polymorphisms was found to be uneven across and within the rice chromosomes. One-fourth of the SNPs and InDels were detected in genic regions, and about 3.5% of the total SNPs resulted in nonsynonymous changes. Large-effect SNPs and InDels, which affect the integrity of the encoded protein, were also identified. Further, we identified DNA polymorphisms present in the differentially expressed genes within the known quantitative trait loci. Among these, a total of 548 SNPs in 232 genes, located in the conserved functional domains, were identified. The data presented in this study provide functional markers and promising target genes for salinity and drought tolerance and present a valuable resource for high-throughput genotyping and molecular breeding for abiotic stress traits in rice.

Marker-assisted Backcrossing for Identification of Salt Tolerant Rice Lines

SSR or microsatellite markers are proved to be ideal for making genetic maps, assisting selection and studying genetic diversity in germplasm. SSR markers are playing important role to identify gene for salt tolerance that can be helpful for plant breeders to develop new cultivars. The experiment was conducted during the period from July 2009 to November 2010 in the experimental field and Biotechnology Laboratory of Plant Breeding Division, Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh to identify salt tolerant rice line of BC1F1 progenies of Binadhan-5 x FL-478 using SSR markers. Salt tolerant genotype, FL-478 was crossed with high yielding variety, Binadhan-5. Randomly selected 40 BC1F1 progenies along with their two parents (Binadhan-5, FL-478 and F1) were genotyped with microsatellite or SSR markers for identification of salt tolerant rice lines. Parental polymorphism survey was assayed by 10 SSR markers and three polymorphic SSR markers viz., RM 336, RM 510, and RM 585 were selected to evaluate BC1F1 rice lines for salt tolerance. In respect of Primer RM 336, 11 lines were found as salt tolerant and 25 lines were heterozygous and 3 lines were susceptible. Primer RM 510 identified two tolerant, 14 heterozygous and 22 susceptible lines. And primer RM 585 identified 4 lines as tolerant and 35 lines as susceptible. Thus, these markers could be efficiently used in tagging salt tolerant genes, in marker-assisted selection and quantitative trait loci (QTL) mapping. The selected BC1F1 could be used for developing BC2F1 and BC2F2 and mapping genes for salinity tolerance. DOI: http://dx.doi.org/10.3329/ijarit.v2i2.14008 Int. J. Agril. Res. Innov. &amp; Tech. 2 (2): 1-8, December, 2012

Biotechnological Tools for the Conservation and Enhancement of Coastal Ecosystem

Coastal ecosystem that forms a connecting link between the terrestrial and aquatic systems is one of the productive systems with implications on coastal resource preservation and sustenance of livelihoods of large dependent communities. With more than 7,500 km of coastline and two island systems, conservation and enhancement of coastal ecosystems have assumed priority. The prospects of sea level rise due to global warming have necessitated concrete attention that are required for ensuring sustainability of this productive system. Use of advanced tools of biotechnology and genetics are of significant relevance in management of productive mangrove resources. In this communication, we have reviewed how the molecular marker technologies have been effectively utilised for assessing the nature and extent of diversity among the mangrove species, the phylogenetic relationships of the group of species as well as developing species specific identification systems. These studies have provided insight into developing conservation strategy for species as well as habitats. The mangrove species has also been effectively utilised for identification and characterisation of salinity tolerant genes and their utilisation for developing location specific crop varieties for abiotic stress tolerance. Use of seawater for cultivation of halophytes as a source of income generating activity in saline land is also discussed.

Pea lectin receptor-like kinase promotes high salinity stress tolerance in bacteria and expresses in response to stress in planta.

The plant lectin receptor-like kinases (LecRLKs) are involved in various signaling pathways but their role in salinity stress tolerance has not heretofore been well described. Salinity stress negatively affects plant growth/productivity and threatens food security worldwide. Based on functional gene-mining assay, we have isolated 34 salinity tolerant genes out of one million Escherichia coli (SOLR) transformants containing pea cDNAs grown in 0.8 M NaCl. Sequence analysis of one of these revealed homology to LecRLK, which possesses N-myristilation and N-glycosylation sites thus corroborating the protein to be a glycoconjugate. The homology based computational modeling of the kinase domain suggested high degree of conservation with the protein already known to be stress responsive in plants. The NaCl tolerance provided by PsLecRLK to the above bacteria was further confirmed in E. coli (DH5alpha). In planta studies showed that the expression of PsLecRLK cDNA was significantly upregulated in response to NaCl as compared to K(+) and Li(+) ions, suggesting the Na(+) ion specific response. Transcript of the PsLecRLK gene accumulates mainly in roots and shoots. The purified 47 kDa recombinant PsLecRLK-KD (kinase domain) protein has been shown to phosphorylate general substrates like MBP and casein. This study not only suggests the conservation of the cellular response to high salinity stress across prokaryotes and plant kingdom but also provides impetus to develop novel concepts for better understanding of mechanism of stress tolerance in bacteria and plants. It also opens up new avenues for studying practical aspects of plant salinity tolerance for enhanced agricultural productivity.

Isolation of high salinity stress tolerant genes from Pisum sativum by random overexpression in Escherichia coli and their functional validation

Salinity stress is one of the major factors which reduce crop plants growth and productivity resulting in significant economic losses worldwide. Therefore, it would be fruitful to isolate and functionally identify new salinity stress-induced genes for understanding the mechanism and developing salinity stress tolerant plants. Based on functional gene screening assay, we have isolated three salinity tolerant genes out of one million Escherichia coli (SOLR) transformants containing pea cDNAs. Sequence analysis of three of these genes revealed homology to Ribosomal-L30E (RPL30E), Chlorophyll-a/b-binding protein (Chla/bBP) and FIDDLEHEAD (FDH). The salinity tolerance of these genes in bacteria was further confirmed by using another strain of E. coli (DH5α) transformants. The homology based computational modeling of these proteins suggested the high degree of conservation with the conserved domains of their homologous partners. The reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed that the expression of these cDNAs (except the FDH) was upregulated in pea plants in response to NaCl stress. We observed that there was no significant effect of Li+ ion on the expression level of these genes, while an increase in response to K+ ion was observed. Overall, this study provides an evidence for a novel function of these genes in high salinity stress tolerance. The PsFDH showed constitutive expression in planta suggesting that it can be used as constitutively expressed marker gene for salinity stress tolerance in plants. This study brings new direction in identifying novel function of unidentified genes in abiotic stress tolerance without previous knowledge of the genome sequence.

Interpopulation differences in expression of candidate genes for salinity tolerance in winter migrating anadromous brown trout (Salmo trutta L.)

BackgroundWinter migration of immature brown trout (Salmo trutta) into freshwater rivers has been hypothesized to result from physiologically stressful combinations of high salinity and low temperature in the sea.ResultsWe sampled brown trout from two Danish populations entering different saline conditions and quantified expression of the hsp70 and Na/K-ATPases α 1b genes following acclimation to freshwater and full-strength seawater at 2°C and 10°C. An interaction effect of low temperature and high salinity on expression of both hsp70 and Na/K-ATPase α 1b was found in trout from the river entering high saline conditions, while a temperature independent up-regulation of both genes in full-strength seawater was found for trout entering marine conditions with lower salinities.ConclusionOverall our results support the hypothesis that physiologically stressful conditions in the sea drive sea-run brown trout into freshwater rivers in winter. However, our results also demonstrate intra-specific differences in expression of important stress and osmoregulative genes most likely reflecting adaptive differences between trout populations on a regional scale, thus strongly suggesting local adaptations driven by the local marine environment.