Tolerance To High Salinity Stress Research Articles

The Sweet Potato K+ Transporter IbHAK11 Regulates K+ Deficiency and High Salinity Stress Tolerance by Maintaining Positive Ion Homeostasis.

The K+ transporter KT/HAK/KUP (K+ transporter/high-affinity K+/K+ uptake) family has a critical effect on K+ uptake and translocation in plants under different environmental conditions. However, the functional analysis of KT/HAK/KUP members in sweet potatoes is still limited. The present work reported the physiological activity of a new gene, IbHAK11, in the KT/HAK/KUP family in sweet potatoes. IbHAK11 expression increased significantly in the low K+-tolerant line compared with the low K+-sensitive line following treatment with low K+ concentrations. IbHAK11 upregulation promoted root growth in Arabidopsis under low K+ conditions. Under high saline stress, transgenic lines had superior growth and photosynthetic characteristics compared with the wild-type (WT). As for IbHAK11-overexpressing plants, activation of both the non-enzymatic and enzymatic reactive oxygen species (ROS) scavenging systems was observed. Therefore, IbHAK11-overexpressing plants had lower malondialdehyde (MDA) and ROS levels (including H2O2 and O2-) compared with WT under salt-induced stress. We also found that under both low K+ and high salinity conditions, overexpression of IbHAK11 enhanced K+ translocation from the root to the shoot and decreased Na+ absorption in Arabidopsis. Consequently, IbHAK11 positively regulated K+ deficiency and high salinity stresses by regulating K+ translocation and Na+ uptake, thus maintaining K+/Na+ homeostasis in plants.

Overexpression of a DEAD box helicase Psp68 gene and its mutant confers salinity stress tolerance in bacteria

Salinity stress adversely affects crop plant growth and productivity resulting in significant yield losses worldwide. Hence, it is essential to develop stress-tolerant species and as well as to understand the mechanisms behind it. The Psp68 is a DNA and RNA helicase and it is involved in numerous processes including protein synthesis, maintaining the basic activities of the cell, transcriptional activation/repressors, RNA processing, and abiotic stress response. This study evidence that overexpression of Psp68 provides salinity (NaCl and LiCl) stress tolerance in bacteria Escherichia coli bacterium also. Furthermore, the site-directed mutagenesis technique was applied to create three single mutants namely K168A, Q286G and R461Q, and their expression was also checked in response to the above mentioned stresses. Surprisingly, only the overexpression of single mutant R461Q showed high salinity stress tolerance in E. coli. Therefore, this study provides a new tool for developing stress tolerant crop plants and bacteria of agronomic importance in the field of agricultural biotechnology. Bangladesh J. Agri. 2022, 47(2): 17-26

Integrated transcriptomic and metabolic analysis response in gills, hepatopancreas, and muscle metabolism in oriental river prawn Macrobrachium nipponense in response to acute high salinity stress

Salinity is an ecological factor that affects the physiological metabolism, survival, and distribution of crustaceans. Although some crustaceans can tolerate an extensive range of salinity, drastic fluctuations can induce damage and even cause death. The oriental river prawn, Macrobrachium nipponense, is a major commercial aquaculture species in China, Japan, and Southeast Asian countries and can survive in a salinity range of 7–20. To explore the metabolic responses and molecular mechanisms of salinity tolerance in M. nipponense, a liquid chromatography–mass spectrometry-based metabolomic analysis and high-throughput RNA sequencing were combined to evaluate the metabolic effects and primary regulatory pathways in gills, hepatopancreas, and muscle of M. nipponense in response to acute high salinity stress in a time-dependent manner. Differentially expressed genes (DGEs) were identified, and total of 632, 836, and 1246 DEGs with a cutoff of significant two-fold change were differentially expressed in hepatopancreas, gills, and muscle tissues, respectively. The DEGs of hepatopancreas and gill tissues were mainly enriched in PPAR signaling pathway, longevity regulating pathway, protein digestion and absorption, and the DEGs of muscle tissue in arginine biosynthesis, adrenergic signaling in cardiomyocytes, cardiac muscle contraction, and cGMP-PKG signaling pathway. The transcriptomic response suggested that M. nipponense exposed to acute high salinity stress may regulate mechanisms related to ion exchange, metabolism, and immune responses to adapt to the environmental alteration. Through LC-MS analysis, 1432 metabolites (589 negative and 843 positive metabolites) were identified. Metabolomic analysis revealed that multiple amino acids and fatty acids were affected. Integrated transcriptome and metabolome analyses indicated that 16 pathways were identified in three tissues of M. nipponense. In addition, 24 metabolites and 34 related DEGs were recorded. Hence, salinity exposure affected metabolic processes in M. nipponense and a higher expression of aminophospholipid genes and enhanced fatty acids may be related to strengthening tolerance to acute high salinity. Overall, these results provide valuable insights into the mechanisms underlying acute high salinity stress responses and tolerance in M. nipponense.

Overexpression of MxbHLH18 Increased Iron and High Salinity Stress Tolerance in Arabidopsis thaliana.

In the life cycle of apple, it will suffer a variety of abiotic stresses, such as iron stress and salt stress. bHLH transcription factors (TFs) play an indispensable role in the response of plants to stress. In this study, a new bHLH gene named MxbHLH18 was separated from Malus xiaojinensis. According to the results of subcellular localization, MxbHLH18 was localized in the nucleus. Salt stress and iron stress affected the expression of MxbHLH18 in Malus xiaojinensis seedlings to a large extent. Due to the introduction of MxbHLH18, the resistance of Arabidopsis thaliana to salt, high iron and low iron was significantly enhanced. Under the environmental conditions of high iron and low iron, the overexpression of MxbHLH18 increased many physiological indexes of transgenic Arabidopsis compared to wild type (WT), such as root length, fresh weight and iron content. The high level expression of MxbHLH18 in transformed Arabidopsis thaliana can not only increased the content of chlorophyll and proline, as well as increasing the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT); it also reduced the content of malondialdehyde (MDA), which was more obvious under high salt conditions. In addition, the relative conductivity, H2O2 content and O2− content in transgenic Arabidopsis decreased under salt stress. Meanwhile, MxbHLH18 can also regulate the expression of downstream genes associated with salt stress (AtCBF1/2/3, AtKIN1 and AtCOR15a/b) and iron stress (AtIRT1, AtFRO2, AtNAS2, ATACT2, AtZIF1 and AtOPT3). Therefore, MxbHLH18 can actively promote the adaptability of plants to the growth environment of salt and low and/or iron.

Overexpression of MxWRKY53 increased iron and high salinity stress tolerance in Arabidopsis thaliana

Overexpression of MxWRKY53 increased iron and high salinity stress tolerance in Arabidopsis thaliana

Exogenous ethanol treatment alleviates oxidative damage of Arabidopsis thaliana under conditions of high-light stress.

Abiotic stresses, such as high light and salinity, are major factors that limit crop productivity and sustainability worldwide. Chemical priming is a promising strategy for improving the abiotic stress tolerance of plants. Recently, we discovered that ethanol enhances high-salinity stress tolerance in Arabidopsis thaliana and rice by detoxifying reactive oxygen species (ROS). However, the effect of ethanol on other abiotic stress responses is unclear. Therefore, we investigated the effect of ethanol on the high-light stress response. Measurement of chlorophyll fluorescence showed that ethanol mitigates photoinhibition under high-light stress. Staining with 3,3'-diaminobenzidine (DAB) showed that the accumulation of hydrogen peroxide (H2O2) was inhibited by ethanol under high-light stress conditions in A. thaliana. We found that ethanol increased the gene expressions and enzymatic activities of antioxidative enzymes, including ASCORBATE PEROXIDASE1 (AtAPX1), Catalase (AtCAT1 and AtCAT2). Moreover, the expression of flavonoid biosynthetic genes and anthocyanin contents were upregulated by ethanol treatment during exposure to high-light stress. These results imply that ethanol alleviates oxidative damage from high-light stress in A. thaliana by suppressing ROS accumulation. Our findings support the hypothesis that ethanol improves tolerance to multiple stresses in field-grown crops.

Transcriptome Analysis of Arabidopsis thaliana Plants Treated with a New Compound Natolen128, Enhancing Salt Stress Tolerance.

Salinity stress is a major threat to agriculture and global food security. Chemical priming is a promising approach to improving salinity stress tolerance in plants. To identify small molecules with the capacity to enhance salinity stress tolerance in plants, chemical screening was performed using Arabidopsis thaliana. We screened 6400 compounds from the Nagoya University Institute of Transformative Bio-Molecule (ITbM) chemical library and identified one compound, Natolen128, that enhanced salinity-stress tolerance. Furthermore, we isolated a negative compound of Natolen128, namely Necolen124, that did not enhance salinity stress tolerance, though it has a similar chemical structure to Natolen128. We conducted a transcriptomic analysis of Natolen128 and Necolen124 to investigate how Natolen128 enhances high-salinity stress tolerance. Our data indicated that the expression levels of 330 genes were upregulated by Natolen128 treatment compared with that of Necolen124. Treatment with Natolen128 increased expression of hypoxia-responsive genes including ethylene biosynthetic enzymes and PHYTOGLOBIN, which modulate accumulation of nitric oxide (NO) level. NO was slightly increased in plants treated with Natolen128. These results suggest that Natolen128 may regulate NO accumulation and thus, improve salinity stress tolerance in A. thaliana.

Overexpression of a Malus xiaojinensis WRKY transcription factor gene (MxWRKY55) increased iron and high salinity stress tolerance in Arabidopsis thaliana

Apple, as one of the most important economic forest tree species, is widely grown in the world. Abiotic stresses, such as high salinity and iron deficiency, affect apple growth and development. WRKY transcription factors (TFs) are widely involved in the responses of plants to adverse stresses. In the present study, a new WRKY gene was isolated from Malus xiaojinensis and designated as MxWRKY55. Subcellular localization showed that MxWRKY55 was localized to the nucleus. The expression level of MxWRKY55 was highly affected by salt, low-Fe, and high-Fe stresses in M. xiaojinensis seedlings. When MxWRKY55 was introduced into Arabidopsis thaliana, it greatly enhanced the salt and Fe tolerance. When dealt with high- and low-Fe stresses, the overexpression of MxWRKY55 in transgenic A. thaliana resulted in higher levels of root length and fresh weight as well as contents of chlorophyll and Fe than wild type (WT). Increased expression of MxWRKY55 in transformed A. thaliana also contributed to higher contents of chlorophyll and proline and higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while malondialdehyde (MDA) content was lower, especially in response to salt stress. Therefore, these results show that MxWRKY55 plays a positive role in the process of plant resistance to salt, low-Fe, and high-Fe stresses.

The protective effects of polyamines on salinity stress tolerance in foxtail millet (Setaria italica L.), an important C4 model crop.

Soil salinity is a major abiotic stress that adversely affects crop growth, development and productivity worldwide. In this study, the individual and synergistic roles of putrescine (Put) and spermidine (Spd) in salinity stress tolerance of foxtail millet (Setaria italica L.) was assessed. In the present study, plants treated with combined biogenic amines Put + Spd possess very efficient antioxidant enzyme systems which help to control the uninhibited oxidation and protect the plants from oxidative damage by ROS scavenging. Additionally, lower concentration of Put + Spd under NaCl stress showed reduced hydrogen peroxide, electrolyte leakage and caspase-like activity than control. FTIR analysis underlying the ability of PAs induced tolerance and the chemical bonds of Put + Spd treated plants were reminiscent of control plants. Moreover, histochemical analysis with 2',7'-dichlorofluorescein diacetate (DCF-DA), 3,3'-Diaminobenzidine (DAB) and nitrotetrazolium blue chloride (NBT) revealed that ROS accumulation was inhibited by combined PAs under salt stress condition. These results showed that Put + Spd significantly improve the endogenous PAs, which enhance high-salinity stress tolerance by detoxifying ROS. For the first time, the synergistic ROS scavenging ability of Put along with Spd was investigated upon salinity tolerance in C4 model foxtail millet crop. Overall, our findings illustrated the implication for improving salinity tolerance of agronomically important crop species.

Extended TAQing system for large-scale plant genome reorganization.

We previously developed a large-scale genome restructuring technology called the TAQing system. It can induce genomic rearrangements by introducing transient and conditional formation of DNA double-strand breaks (DSBs) via heat activation of a restriction enzyme TaqI, which can cleave DNA at 5'-TCGA-3' sequences in the genome at higher temperatures (37-42°C). Such heat treatment sometimes confers lethal damage in certain plant species and TaqI cannot induce rearrangements in AT-rich regions. To overcome such problems we developed an extended TAQing (Ex-TAQing) system, which enables the use of a wider range of restriction enzymes active at standard plant-growing temperatures. We established the Ex-TAQing system using MseI that can efficiently cleave DNA at room temperature (at temperatures ranging from 22 to 25°C) and the 5'-TTAA-3' sequence which is highly abundant in the Arabidopsis genome. A synthetic intron-spanning MseI gene, which was placed downstream of a heat-shock-inducible promoter, was conditionally expressed upon milder heat treatment (33°C) to generate DSBs in Arabidopsis chromosomes. Genome resequencing revealed various types of genomic rearrangements, including copy number variations, translocation and direct end-joining at MseI cleavage sites. The Ex-TAQing system could induce large-scale rearrangements in diploids more frequently (17.4%, n=23) than the standard TAQing system. The application of this system to tetraploids generated several strains with chromosomal rearrangements associated with beneficial phenotypes, such as high salinity stress tolerance and hypersensitivity to abscisic acid. We have developed the Ex-TAQing system, allowing more diverse patterns of genomic rearrangements, by employing various types of endonucleases and have opened a way to expand the capacity for artificial genome reorganization.

Inhibition of mitochondrial complex I by the novel compound FSL0260 enhances high salinity-stress tolerance in Arabidopsis thaliana

Chemical priming is an attractive and promising approach to improve abiotic stress tolerance in a broad variety of plant species. We screened the RIKEN Natural Products Depository (NPDepo) chemical library and identified a novel compound, FSL0260, enhancing salinity-stress tolerance in Arabidopsis thaliana and rice. Through transcriptome analysis using A. thaliana seedlings, treatment of FSL0260 elevated an alternative respiration pathway in mitochondria that modulates accumulation of reactive oxygen species (ROS). From comparison analysis, we realized that the alternative respiration pathway was induced by treatment of known mitochondrial inhibitors. We confirmed that known inhibitors of mitochondrial complex I, such as rotenone and piericidin A, also enhanced salt-stress tolerance in Arabidopsis. We demonstrated that FSL0260 binds to complex I of the mitochondrial electron transport chain and inhibits its activity, suggesting that inhibition of mitochondrial complex I activates an alternative respiration pathway resulting in reduction of ROS accumulation and enhancement of tolerance to salinity in plants. Furthermore, FSL0260 preferentially inhibited plant mitochondrial complex I rather than a mammalian complex, implying that FSL0260 has a potential to be an agent for improving salt-stress tolerance in agriculture that is low toxicity to humans.

English

Soil salinity is a growing problem on many irrigated parts of arid and semi-arid areas of Ethiopia. Utilization of improved salt-tolerant forage grasses help farmers to maximize production and reclaim saline soil. A study was conducted at Werer Agricultural Research Center (WARC) from 2012 to 2014 to evaluate performance of four forage grass species of salinity tolerance, ameliorative effect and biomass production. The result showed that dry matter yield obtained under saline soil was higher in Cinchrus ciliaris (37 ton/ha/year) followed by Chloris gayana (36 ton/ha/year), while the smallest was recorded from Sorghum sudanese (27 ton/ha/year). After exposing for salt stress, C. gayana and C. ciliaris dry matter production relative to normal soil only decrease by 15 and 9%, respectively. While, Panicum antidotale and S. sudanese dry matter reduction was Severe, by 53 and 45%, respectively. Reduction in electrical conductivity (ECe) varied between 52.60 and 74.81% in the upper 0 to 30 cm soil layer and 54.76 to 79.63% in the lower 30 to 60 cm. The highest reduction percentage of salinity under surface (74.81%) and sub-surface (79.63%) layer soil occurred under C. gayana grass. C. ciliaris, P. antidotale and S. sudanese cause the reduction at surface soil layer ECe by 70.55, 66.42 and 54.76%, respectively. The same trend was observed for reduction of ESP and pHe as a result of growing of grass species. Generally, C. gayana and C. ciliaris have excellent potential for its high salinity stress tolerance, biomass production and ameliorative effect on soil properties. Key words: Salinity, amelioration, forage grasses, biomass yield.

The duration of ethanol-induced high-salinity stress tolerance in Arabidopsis thaliana

ABSTRACTHigh-salinity stress affects plant growth and crop yield, so the development of techniques to enhance plant tolerance to such stress is important. Recently, we revealed that ethanol enhances high-salinity stress tolerance in Arabidopsis thaliana and rice by detoxifying Reactive Oxygen Species (ROS). However, we did not investigate how long salt stress tolerance was maintained following treatment with ethanol. Therefore, we herein analyzed survival rates and expression levels of AtZAT12, which is a transcriptional factor of ROS detoxification enzymes, under different conditions in Arabidopsis. Our results showed that ethanol-mediated high-salinity stress tolerance was lost after a 24 h break in ethanol treatment in ~ 1-week-old plants. Although ethanol enhanced salt stress tolerance, high concentrations of ethanol negatively affected plant growth. Thus, these data support the idea that adjustments of the frequency and amount of ethanol application to plants is useful to enhance salt stress tolerance without growth inhibition in the agricultural field.

Transcriptomic analysis of Arabidopsis thaliana plants treated with the Ky-9 and Ky-72 histone deacetylase inhibitors

ABSTRACTHistone acetylation plays a pivotal role in plant growth and development, and is regulated by the antagonistic relationship between histone acetyltransferase (HAT) and histone deacetylase (HDAC). We previously revealed that some HDAC inhibitors confer high-salinity stress tolerance in plants. In this study, we identified two HDAC inhibitors, namely Ky-9 and Ky-72, which enhanced the high-salinity stress tolerance of Arabidopsis thaliana. Ky-9 and Ky-72 are structurally similar chlamydocin analogs. However, the in vitro inhibitory activity of Ky-9 against mammalian HDAC is greater than that of Ky-72. A western blot indicated that Ky-9 and Ky-72 increased the acetylation levels of histone H3, suggesting they exhibit HDAC inhibitory activities in plants. We conducted a transcriptomic analysis to investigate how Ky-9 and Ky-72 enhance high-salinity stress tolerance. Although Ky-9 upregulated the expression of more genes than Ky-72, similar gene expression patterns were induced by both HDAC inhibitors. Additionally, the expression of high-salinity stress tolerance-related genes, such as anthocyanin-related genes and a small peptide-encoding gene, increased by Ky-9 and Ky-72. These data suggest that slight structural differences in chemical side chain between HDAC inhibitors can alter inhibitory effect on HDAC protein leading to influence gene expression, thereby enhancing high-salinity stress tolerance in different extent.

Ethanol Enhances High-Salinity Stress Tolerance by Detoxifying Reactive Oxygen Species in Arabidopsis thaliana and Rice.

High-salinity stress considerably affects plant growth and crop yield. Thus, developing techniques to enhance high-salinity stress tolerance in plants is important. In this study, we revealed that ethanol enhances high-salinity stress tolerance in Arabidopsis thaliana and rice. To elucidate the molecular mechanism underlying the ethanol-induced tolerance, we performed microarray analyses using A. thaliana seedlings. Our data indicated that the expression levels of 1,323 and 1,293 genes were upregulated by ethanol in the presence and absence of NaCl, respectively. The expression of reactive oxygen species (ROS) signaling-related genes associated with high-salinity tolerance was upregulated by ethanol under salt stress condition. Some of these genes encode ROS scavengers and transcription factors (e.g., AtZAT10 and AtZAT12). A RT-qPCR analysis confirmed that the expression levels of AtZAT10 and AtZAT12 as well as AtAPX1 and AtAPX2, which encode cytosolic ascorbate peroxidases (APX), were higher in ethanol-treated plants than in untreated control plants, when exposure to high-salinity stress. Additionally, A. thaliana cytosolic APX activity increased by ethanol in response to salinity stress. Moreover, histochemical analyses with 3,3′-diaminobenzidine (DAB) and nitro blue tetrazolium (NBT) revealed that ROS accumulation was inhibited by ethanol under salt stress condition in A. thaliana and rice, in which DAB staining data was further confirmed by Hydrogen peroxide (H2O2) content. These results suggest that ethanol enhances high-salinity stress tolerance by detoxifying ROS. Our findings may have implications for improving salt-stress tolerance of agriculturally important field-grown crops.

Ky-2, a Histone Deacetylase Inhibitor, Enhances High-Salinity Stress Tolerance in Arabidopsis thaliana.

Adaptation to environmental stress requires genome-wide changes in gene expression. Histone modifications are involved in gene regulation, but the role of histone modifications under environmental stress is not well understood. To reveal the relationship between histone modification and environmental stress, we assessed the effects of inhibitors of histone modification enzymes during salinity stress. Treatment with Ky-2, a histone deacetylase inhibitor, enhanced high-salinity stress tolerance in Arabidopsis. We confirmed that Ky-2 possessed inhibition activity towards histone deacetylases by immunoblot analysis. To investigate how Ky-2 improved salt stress tolerance, we performed transcriptome and metabolome analysis. These data showed that the expression of salt-responsive genes and salt stress-related metabolites were increased by Ky-2 treatment under salinity stress. A mutant deficient in AtSOS1(Arabidopis thaliana SALT OVERLY SENSITIVE 1), which encodes an Na(+)/H(+)antiporter and was among the up-regulated genes, lost the salinity stress tolerance conferred by Ky-2. We confirmed that acetylation of histone H4 at AtSOS1 was increased by Ky-2 treatment. Moreover, Ky-2 treatment decreased the intracellular Na(+)accumulation under salinity stress, suggesting that enhancement of SOS1-dependent Na(+)efflux contributes to increased high-salinity stress tolerance caused by Ky-2 treatment.

Rice ASR1 has function in abiotic stress tolerance during early growth stages of rice

OsASR1 expression was induced through Abscisic acid (ABA) and stress treatments in leaves. The constitutive overexpression of OsASR1 in rice reduced ABA sensitivity, and increased high salinity and osmotic stress tolerance in early growth stages. These results indicated that OsASR1 has function in abiotic stress tolerance during early growth stages of rice.

Biochemical composition and performance of Atlantic cod ( Gadus morhua L.) eggs and larvae obtained from farmed and wild broodstocks

Farming of Atlantic cod, Gadus morhua L., has been facing several challenges lately. Biological issues such as differences in egg quality and lack of high quality larvae are considered as prominent limiting factors. The aim of this study was to compare fertilization and hatching rates, incidence of malformed larvae at hatching, larval viability (high-salinity stress and starvation tolerance tests) and the biochemical profile (proteins, amino acids, lipids, fatty acids and minerals) between eggs produced from wild and farmed broodstocks. Twenty-five batches of eggs from farmed broodstock (FB) and 27 egg batches from wild broodstock (WB) were collected during the reproductive season. Fertilization and hatching rates were significantly higher in WB group (91 ± 3% and 86 ± 3%, respectively) than in FB (75 ± 3% and 66 ± 3%, respectively). In high-salinity stress test, WB larvae survived for a significantly longer time than FB larvae. No differences between egg batches from the two broodstocks were observed in starvation tolerance tests, incidence of malformed larvae at hatching, as well as in the total content of proteins, lipids, fatty acids, zinc, and calcium concentrations. Regarding fatty acids, FB eggs had significantly higher levels of C16:0, C18:0, C18:2n − 6, C18:3n − 3, C18:3n − 6, C20:4n − 6, C20n:5n − 3, C22:5n − 3 and C22:5n − 6, whereas WB eggs had significantly higher levels of C14:0, C16:1n − 7, C18:4n − 3, C20:4n − 3, C22:6n − 3 and C24:1n − 9. As for the amino acid profile, WB eggs had significantly higher levels of aspartic acid, serine, glycine, threonine, taurine and leucine, while FB eggs had significantly higher levels of proline, tryptophan, phenylalanine and arginine. The concentrations of minerals such as copper and phosphorus were significantly higher in WB eggs, whereas in FB eggs iron concentration was significantly higher. Overall, the biological parameters indicated that egg and larvae originating from WB were of superior quality than those from FB. The information on the biochemical profile may be useful in improving the quality of broodstock feeds for Atlantic cod.

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.