Salt Stress-responsive Proteins Research Articles

The fungus Acremonium alternatum enhances salt stress tolerance by regulating host redox homeostasis and phytohormone signaling.

While endophytic fungi offer promising avenues for bolstering plant resilience against abiotic stressors, the molecular mechanisms behind this biofortification remain largely unknown. This study employed a multifaceted approach, combining plant physiology, proteomic, metabolomic, and targeted hormonal analyses to illuminate the early response of Brassica napus to Acremonium alternatum during the nascent stages of their interaction. Notably, under optimal growth conditions, the initial reaction to fungus was relatively subtle, with no visible alterations in plant phenotype and only minor impacts on the proteome and metabolome. Interestingly, the identified proteins associated with the Acremonium response included TUDOR 1, Annexin D4, and a plastidic K+ efflux antiporter, hinting at potential processes that could counter abiotic stressors, particularly salt stress. Subsequent experiments validated this hypothesis, showcasing significantly enhanced growth in Acremonium-inoculated plants under salt stress. Molecular analyses revealed a profound impact on the plant's proteome, with over 50% of salt stress response proteins remaining unaffected in inoculated plants. Acremonium modulated ribosomal proteins, increased abundance of photosynthetic proteins, enhanced ROS metabolism, accumulation of V-ATPase, altered abundances of various metabolic enzymes, and possibly promoted abscisic acid signaling. Subsequent analyses validated the accumulation of this hormone and its enhanced signaling. Collectively, these findings indicate that Acremonium promotes salt tolerance by orchestrating abscisic acid signaling, priming the plant's antioxidant system, as evidenced by the accumulation of ROS-scavenging metabolites and alterations in ROS metabolism, leading to lowered ROS levels and enhanced photosynthesis. Additionally, it modulates ion sequestration through V-ATPase accumulation, potentially contributing to the observed decrease in chloride content.

Insights concerning advancing the agroecological sustainability of salinity tolerance through proteomics profiling of hexaploid wheat (Triticum aestivum L.)

Wheat plays a significant role in the provision of food and nutrition. However, rapid soil salinization poses a severe threat to its production worldwide. Salt stress stunts wheat growth and quality, resulting in low grain yields. The adaptation of wheat to salinity involves complex physio-biochemical and molecular mechanisms. This study aimed to identify the genetic approaches concerning salt stress-responsive proteins and protein pathways in wheat roots under controlled (0 mM) and NaCl stress (250 mM) solution using label-free proteomic quantification analysis. We found a significant accumulation of Na+ in the leaf and root compared with the controlled condition. Besides, we identified 2436 proteins enhanced under salt stress, with 198 differentially abundant proteins (DAPs), including 170 up-regulated and 28 down-regulated proteins. Many of these proteins were involved in salinity tolerance, including heat shock proteins, glutathione S-transferase, dehydrin, peroxidase, potassium channel beta subunit-type H+-ATPase, superoxide dismutase (Cu-Zn), 14-3-3 protein, peroxidase, malate dehydrogenase, and heat shock proteins. The abundance of a V-type H+ ATPase and 14-3-3 protein was also enhanced, facilitating Na+ compartmentalization in the vacuole through the salt overly sensitive (SOS) pathway. Additionally, many antioxidant enzymes, including peroxidase, glutathione-S-transferase, and thioredoxins, were up-regulated, playing a vital role in detoxifying reactive oxygen species (ROS) in salinity-stressed wheat roots. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses showed that salinity stress enhances the abundance of proteins in several metabolic pathways, such as the citrate cycle, ribosome, oxidative phosphorylation, glycolysis, carbon metabolism, and cytoplasm. We anticipate that the identified proteins under salinity conditions will provide us with a deeper understanding of their application in agriculture biotechnology.

Salt stress proteins in plants: An overview.

Salinity stress is considered the most devastating abiotic stress for crop productivity. Accumulating different types of soluble proteins has evolved as a vital strategy that plays a central regulatory role in the growth and development of plants subjected to salt stress. In the last two decades, efforts have been undertaken to critically examine the genome structure and functions of the transcriptome in plants subjected to salinity stress. Although genomics and transcriptomics studies indicate physiological and biochemical alterations in plants, it do not reflect changes in the amount and type of proteins corresponding to gene expression at the transcriptome level. In addition, proteins are a more reliable determinant of salt tolerance than simple gene expression as they play major roles in shaping physiological traits in salt-tolerant phenotypes. However, little information is available on salt stress-responsive proteins and their possible modes of action in conferring salinity stress tolerance. In addition, a complete proteome profile under normal or stress conditions has not been established yet for any model plant species. Similarly, a complete set of low abundant and key stress regulatory proteins in plants has not been identified. Furthermore, insufficient information on post-translational modifications in salt stress regulatory proteins is available. Therefore, in recent past, studies focused on exploring changes in protein expression under salt stress, which will complement genomic, transcriptomic, and physiological studies in understanding mechanism of salt tolerance in plants. This review focused on recent studies on proteome profiling in plants subjected to salinity stress, and provide synthesis of updated literature about how salinity regulates various salt stress proteins involved in the plant salt tolerance mechanism. This review also highlights the recent reports on regulation of salt stress proteins using transgenic approaches with enhanced salt stress tolerance in crops.

How salt stress-responsive proteins regulate plant adaptation to saline conditions.

An overview is presented of recent advances in our knowledge of candidate proteins that regulate various physiological and biochemical processes underpinning plant adaptation to saline conditions. Salt stress is one of the environmental constraints that restrict plant distribution, growth and yield in many parts of the world. Increased world population surely elevates food demands all over the globe, which anticipates to add a great challenge to humanity. These concerns have necessitated the scientists to understand and unmask the puzzle of plant salt tolerance mechanisms in order to utilize various strategies to develop salt tolerant crop plants. Salt tolerance is a complex trait involving alterations in physiological, biochemical, and molecular processes. These alterations are a result of genomic and proteomic complement readjustments that lead to tolerance mechanisms. Proteomics is a crucial molecular tool that indicates proteins expressed by the genome, and also identifies the functions of proteins accumulated in response to salt stress. Recently, proteomic studies have shed more light on a range of promising candidate proteins that regulate various processes rendering salt tolerance to plants. These proteins have been shown to be involved in photosynthesis and energy metabolism, ion homeostasis, gene transcription and protein biosynthesis, compatible solute production, hormone modulation, cell wall structure modification, cellular detoxification, membrane stabilization, and signal transduction. These candidate salt responsive proteins can be therefore used in biotechnological approaches to improve tolerance of crop plants to salt conditions. In this review, we provided comprehensive updated information on the proteomic data of plants/genotypes contrasting in salt tolerance in response to salt stress. The roles of salt responsive proteins that are potential determinants for plant salt adaptation are discussed. The relationship between changes in proteome composition and abundance, and alterations observed in physiological and biochemical features associated with salt tolerance are also addressed.

Identification of Salt Stress-Responsive Proteins in Maize (Zea may) Seedlings Using iTRAQ-Based Proteomic Technique.

Background: Soil salinity is a major abiotic stress that limits plant growth and yield worldwide. Objective: To better understand the mechanism of salt stress adaptation in maize (Zea may), proteomic analysis of maize responses to salt stress were analyzed in seedling.Materials and Methods: Taking maize seedlings untreated and treated with NaCl for 24 h as material, isobaric tags for relative and absolute quantitation (iTRAQ) were used to analyze the protein expression profile of maize seedlings after salt stress.Results: The result showed that 270 differentially expression proteins (DEPs) were identified in maize seedlings after salt stress. The majority proteins had functions related to translation, ribosomal structure and biogenesis (15%), posttranslational modification, protein turnover, chaperones (14%) and others metabolism. Quantitative real-time PCR analysis showed that the EF-Tu, peroxiredoxin, FoF1-type ATP synthase, glutamate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, Acetyl-CoA acetyltransferase and nucleoside diphosphate kinase genes were up-regulated in the adaptation of maize to salt stress.Conclusions: The coped with salt stress of maize seedlings might be included nitrogen and glutamate (Glu) metabolism and energy homeostasis, nucleotide transport and metabolism, soluble sugar, fatty acid and nucleoside triphosphates synthesis. Moreover, the enhancement of plant to scavenge ROS, such as peroxiredoxin, might play significant roles in the adaptation of maize to salt stress.Taken together, these proteins might have important roles in defense mechanisms against salt stress in maize.We hope that this study provides valuable information for the further utilization and study on the molecular mechanisms of defense mechanisms in maize.

Insights from comparative proteomic analysis into degradation of phenanthrene and salt tolerance by the halophilic Martelella strain AD-3

A halophilic PAHs-degrading strain, Martelella AD-3, was previously isolated from highly saline petroleum-contaminated soil. In this study, label-free proteomics were performed to identify differentially expressed proteins (DEPs) under Group P (phenanthrene +5% salinity) and Group G (glycerol +1% salinity), which would help to reveal the mechanism of phenanthrene degradation and salt tolerance. A total of 307 up-regulated DEPs were found in Group P, including 17 phenanthrene degradation proteins. Among these phenanthrene-degrading proteins, the ferredoxin of aromatic ring-hydroxylating dioxygenase (RHD) was up-regulated by 110-fold and gentisate 1,2-dioxygenases (GDOs) were only expressed in Group P. Besides, we also found nine high salt stress response proteins, including ectoine synthase and transport protein of compatible (osmoprotectant) solutes, were differentially up-regulated. These results indicate that strain AD-3 mainly relied on RHD and dihydrodiol dehydrogenase to degrade phenanthrene, and accumulated compatible solutes for resistance to salt stress. This study provides strong theoretical guidance for understanding the degradation of phenanthrene by strain AD-3 in high salt environments.

ITRAQ-based proteomic technique provides insights into salt stress responsive proteins in Apocyni Veneti Folium (Apocynum venetum L.)

Soil salinity is a major abiotic stress that limits plant growth and productivity. Understanding the mechanisms of plant salinity tolerance can facilitate engineering for quality improvement. Apocynum venetum L. exhibits tolerance to salinity. Due to the lack of a genomic database, RNA-seq based transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) based proteomic profiles of Apocyni Veneti Folium (leaves of Apocynum venetum L.) exposure to four levels of salt treatments (0, 100, 200 and 300 mM NaCl, respectively) were performed. A total of 143, 162 and 167 differentially expressed proteins (DEPs) were found between salt-treated Apocyni Veneti Folium compared with control, respectively. They were mainly involved in carbohydrate and energy metabolism, biosynthesis of metabolites and signal transduction. Furthermore, results showed that carbon and nitrogen metabolisms were altered under salt stress; low and moderate levels of salt stress enhanced photosynthetic functions and ramped up carbohydrate metabolism. However, severe salt stress depressed biosynthesis of secondary metabolites, consistent with the metabolomics results. It is worth emphasizing that some key salt-responsive proteins, such as dehydrin 1, annexin, pathogenesis-related protein, prolyl oligopeptidase, peroxidase, cinnamyl alcohol dehydrogenase, 4-hydroxycinnamoyl-CoA ligase 3, cytochrome P450 CYP73A120, were screened. These novel proteins provide a good starting point for further research into their functions using genetic or other approaches. In addition, a weak correlation between the abundance of DEPs and the corresponding differentially expressed genes highlighted the effect of post-transcriptional modifications and the importance of employing proteomics and transcriptomics to analyze global protein level changes. In conclusion, the protein profiles indicate that halophyte uses a multipronged approach to overcome salt stress, and provides some novel information on revealing the mechanisms of adaption and quality formation.

Retraction Note to: Integrated physiological and proteomic analysis of embryo and endosperm reveals central salt stress response proteins during seed germination of winter wheat cultivar Zhengmai 366

The editor has retracted this article [1] because parts of Figs. 1 and 4 were duplicated from a previously published paper by the same authors [2] without appropriate disclosure. None of the authors have responded to any correspondence from the editor about publication of this retraction notice.

Salt Stress-Responsive Protein Interaction in Hordeum vulgare

Salt stress affects crop productivity by altering the biology of the plant and limiting productivity. Hordeum vulgare is the most tolerant cereal crop, with rich genetic resources. The underlying molecular mechanism involved in salt stress response is yet to be comprehensively addressed. A total of 305 proteins are involved in the network. We attempted to find relationships between a few representative stress-responsive proteins of osmotic (pip1), ionic (K+/Na+ ratio in the leaf sheath, HvHAK, HAK4, NHX1 and Ha1), and oxidative stress (APX, CAT1, SOD1) from the public protein database to identify the most influential protein in the network. Further, the salt response proteins were analyzed for their enriched protein domains, Kyoto Encyclopedia of Genes and Genomes pathways, molecular functions, and cell localization. The graph theory analysis of the large data could provide clues for the identification of potential biomarkers for salt stress in barley. An experiment was performed in three accessions of H. vulgare to identify the reliability of the theoretical network relationship in biological systems. The expression of the above-mentioned proteins was further experimentally proven based on the expression and assay.

RETRACTED ARTICLE: Integrated physiological and proteomic analysis of embryo and endosperm reveals central salt stress response proteins during seed germination of winter wheat cultivar Zhengmai 366

BackgroundSalinity is a major abiotic stressor that affects seed germination, plant growth, and crop production. Seed germination represents the beginning of plant growth and is closely linked with subsequent crop development and ultimate yield formation. This study attempted to extend findings regarding the potential proteomic dynamics during wheat seed germination under salt stress and to explore the mechanism of crop salt response.ResultsSalt stress significantly affected seed physiological activities during the germination process, resulting in significant decreases in phytohormone and α-amylase activity and significant increases in soluble sugar, starch, and ADP glucose pyrophosphorylase activity. A comparative proteomics approach was applied to analyze the dynamic proteome changes of embryo and endosperm during seed germination in Chinese winter wheat cultivar Zhengmai 366 under salt stress. Two-dimensional electrophoresis identified 92 and 61 differentially accumulated proteins (DAPs) in response to salt stress in embryo and endosperm, respectively. Both organs contained a high proportion of DAPs involved in stress defense, energy metabolism, and protein/amino acid metabolism. The endosperm had more DAPs related to storage proteins and starch metabolism than the embryo, and 2% of DAPs participating in lipid and sterol metabolism were specifically detected in the embryo.ConclusionsSeed physiological activities were significantly affected during the germination process when subjected to salt stress. The DAPs involved in stress defense and energy metabolism were upregulated whereas those related to reserve substance degradation and protein/amino acid metabolism were significantly downregulated, leading to delayed seed germination under salt stress. Our proteomic results revealed synergistic regulation of the response to salt stress during seed germination.

OsRACK1A, encodes a circadian clock-regulated WD40 protein, negatively affect salt tolerance in rice

The receptor for activated C kinase 1 (RACK1) is a WD40 type protein that is involved in multiple signaling pathways and is conserved from prokaryotes to eukaryotes. Here we report that rice RACK1A (OsRACK1A) is regulated by circadian clocks and plays an important role in the salt stress response. OsRACK1A was found to follow a rhythmic expression profile under circadian conditions at both the transcription and the translation levels, although the expression was arrhythmic under salt stress. Analysis of plant survival rates, fresh weight, proline content, malondialdehyde, and chlorophyll showed that suppression of OsRACK1A enhanced tolerance to salt stress. The ion concentration in both roots and leaves revealed that OsRACK1A-suppressed transgenic rice could maintain low Na+ and high K+ concentrations. Furthermore, OsRACK1A-suppressed transgenic rice accumulated significantly more abscisic acid (ABA) and more transcripts of ABA- and stress-inducible genes compared with the wild-type plants. Real-time quantitative polymerase chain reaction analysis revealed that many stress-related genes, including APETALA 2/Ethylene Responsive Factor (AP2/ERF) transcription factors, were upregulated in the OsRACK1A-suppressed transgenic rice line. We identified putative interactors of OsRACK1A, and found that OsRACK1A interacted with many salt stress-responsive proteins directly. These results suggest that OsRACK1A is regulated by circadian rhythm, and involved in the regulation of salt stress responses.

Integration of proteomic and transcriptomic profiles reveals multiple levels of genetic regulation of salt tolerance in cotton

BackgroundSalinity is a major abiotic stress that limits upland cotton growth and reduces fibre production worldwide. To reveal genetic regulation via transcript and protein levels after salt stress, we comprehensively analysed the global changes in mRNA, miRNA, and protein profiles in response to salt stress in two contrasting salt-tolerant cotton genotypes.ResultsIn the current study, proteomic and mRNA-seq data were combined to reveal that some genes are differentially expressed at both the proteomic and mRNA levels. However, we observed no significant change in mRNA corresponding to most of the strongly differentially abundant proteins. This finding may have resulted from global changes in alternative splicing events and miRNA levels under salt stress conditions. Evidence was provided indicating that several salt stress-responsive proteins can alter miRNAs and modulate alternative splicing events in upland cotton. The results of the stringent screening of the mRNA-seq and proteomic data between the salt-tolerant and salt-sensitive genotypes identified 63 and 85 candidate genes/proteins related to salt tolerance after 4 and 24 h of salt stress, respectively, between the tolerant and sensitive genotype. Finally, we predicted an interaction network comprising 158 genes/proteins and then discovered that two main clusters in the network were composed of ATP synthase (CotAD_74681) and cytochrome oxidase (CotAD_46197) in mitochondria. The results revealed that mitochondria, as important organelles involved in energy metabolism, play an essential role in the synthesis of resistance proteins during the process of salt exposure.ConclusionWe provided a plausible schematic for the systematic salt tolerance model; this schematic reveals multiple levels of gene regulation in response to salt stress in cotton and provides a list of salt tolerance-related genes/proteins. The information here will facilitate candidate gene discovery and molecular marker development for salt tolerance breeding in cotton.

Proteomic analysis of early salt stress responsive proteins in alfalfa roots and shoots

BackgroundAlfalfa (Medicago sativa) is the most extensively cultivated forage legume in the world, and salinity stress is the most problematic environmental factors limiting alfalfa production. To evaluate alfalfa tissue variations in response to salt stress, comparative physiological and proteomic analyses were made of salt responses in the roots and shoots of the alfalfa.MethodA two-dimensional gel electrophoresis (2-DE)-based proteomic technique was employed to identify the differentially abundant proteins (DAPs) from salt-treated alfalfa roots and shoots of the salt tolerance cultivars Zhongmu No 1 cultivar, which was subjected to a range of salt stress concentrations for 9 days. In parallel, REL, MAD and H2O2 contents, and the activities of antioxidant enzymes of shoots and roots were determinand.ResultTwenty-seven spots in the shoots and 36 spots in the roots that exhibited showed significant abundance variations were identified by MALDI-TOF-TOF MS. These DAPs are mainly involved in the biological processes of photosynthesis, stress and defense, carbohydrate and energy metabolism, second metabolism, protein metabolism, transcriptional regulation, cell wall and cytoskeleton metabolism, ion transpor, signal transduction. In parallel, physiological data were correlated well with our proteomic results. It is worth emphasizing that some novel salt-responsive proteins were identified, such as CP12, pathogenesis-related protein 2, harvest-induced protein, isoliquiritigenin 2′-O-methyltransferase. qRT-PCR was used to study the gene expression levels of the four above-mentioned proteins; four patterns are consistent with those of induced protein.ConclusionThe primary mechanisms underlying the ability of alfalfa seedlings to tolerate salt stress were photosynthesis, detoxifying and antioxidant, secondary metabolism, and ion transport. And it also suggests that the different tissues responded to salt-stress in different ways.

FKBP-type peptidyl-prolyl cis-trans isomerase from thermophilic microalga, Scenedesmus sp.: molecular characterisation and demonstration of acquired salinity and thermotolerance in E. coli by recombinant expression

A novel complementary DNA (cDNA) encoding temperature and salt stress-responsive FK506-binding protein 12 (FKBP12), a chaperone with peptidyl-prolyl cis-trans isomerase (PPIase) activity was isolated using suppression subtractive hybridization (SSH) technique from a thermophilic chlorophycean microalga, Scenedesmus sp., isolated from the Manikaran hot springs at Himachal Pradesh, India. To our best knowledge, this is the first report of temperature and salt-responsive FKBP12 isolated from a microalgae. The Scenedesmus FKBP12 (Sce.FKBP12) nucleotide sequence revealed the presence of an open reading frame of 327 bp, encoding 108 amino acid protein containing a single FKBP-like domain with a predicted molecular weight of 12 KDa. Amino acid sequence comparison of Sce.FKBP12 with its ortholog from other eukaryotic organisms showed structural conservation among each other. Expression profile of Sce.FKBP12 gene using quantitative real-time PCR showed significant up-regulated expression under temperature and salinity stress. The recombinant Sce.FKBP12 was over-expressed in Escherichia coli using pET28b expression vector. The recombinant expression of Sce.FKBP12 in E. coli cells imparted temperature and salinity tolerance to the host cells, implying a significant role of Sce.FKBP12 in stress tolerance mechanisms. Sce.FKBP12 could be a promising transgene candidate for imparting abiotic stress tolerance in crop plants, and they need to be further evaluated using plant models like Arabidopsis or Tobacco for confirming its potential as a transgene candidate in development of temperature and salinity-tolerant transgenic crops for improved and sustained productions in adverse agro-climatic conditions.

Physiological Responses and Comparison of Protein Changes in the Leaves of Two Wheat (Triticum aestivumL.) Genotypes by 2-D Electrophoresis Under NaCl Salinity Stress

A pot experiment was conducted to investigate salinity stress related physiological responses and comparison of protein changes in the leaves of two wheat genotypes at CRI (Crown Root Initiation) and booting stages. Physiological approach is a preliminary marker to know the effect of salinity amelioration. MSI (Membrane Stability Index) and RWC (Relative Water Content) of wheat leaves were reduced in salinity susceptible genotype GW-496 than in salinity tolerant genotype GW-173 at both the stages. The results also revealed that MSI and RWC were recorded highest at control condition and lowest @160 mM NaCl treatment at booting stage. In proteomics investigation, gel analysis of the resulting protein patterns revealed genotype specific and salt stress responsive protein expression. Total 419 of protein spots were found under match Id in control as well as in treated tolerant and susceptible genotypes at CRI and booting stage. More number of protein expressions was noticed in the tolerant genotype than in the susceptible genotype at both the stages. The change in physiological parameters varied with genotypes and the crop growth stages. Proteomics results indicate that tolerance to salt stress is associated with changes of protein levels in wheat genotypes. In particular, comparative proteomic investigations of plants before and after specific or interactive stresses allow us to obtain information on how defensive mechanisms are adopted from plants which might be helpful in the development of future strategies against salinity stress.

Identification of early salt stress responsive proteins in seedling roots of upland cotton (Gossypium hirsutum L.) employing iTRAQ-based proteomic technique.

Soil salinity is a major abiotic stress that limits plant growth and agricultural productivity. Upland cotton (Gossypium hirsutum L.) is highly tolerant to salinity; however, large-scale proteomic data of cotton in response to salt stress are still scant. Here, an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic technique was employed to identify the early differentially expressed proteins (DEPs) from salt-treated cotton roots. One hundred and twenty-eight DEPs were identified, 76 of which displayed increased abundance and 52 decreased under salt stress conditions. The majority of the proteins have functions related to carbohydrate and energy metabolism, transcription, protein metabolism, cell wall and cytoskeleton metabolism, membrane and transport, signal transduction, in addition to stress and defense. It is worth emphasizing that some novel salt-responsive proteins were identified, which are involved in cell cytoskeleton metabolism (actin-related protein2, ARP2, and fasciclin-like arabinogalactan proteins, FLAs), membrane transport (tonoplast intrinsic proteins, TIPs, and plasma membrane intrinsic proteins, PIPs), signal transduction (leucine-rich repeat receptor-like kinase encoding genes, LRR-RLKs) and stress responses (thaumatin-like protein, TLP, universal stress protein, USP, dirigent-like protein, DIR, desiccation-related protein PCC13-62). High positive correlation between the abundance of some altered proteins (superoxide dismutase, SOD, peroxidase, POD, glutathione S-transferase, GST, monodehydroascorbate reductase, MDAR, and malate dehydrogenase, MDH) and their enzyme activity was evaluated. The results demonstrate that the iTRAQ-based proteomic technique is reliable for identifying and quantifying a large number of cotton root proteins. qRT-PCR was used to study the gene expression levels of the five above-mentioned proteins; four patterns are consistent with those of induced protein. These results showed that the proteome of cotton roots under NaCl stress is complex. The comparative protein profiles of roots under salinity vs control improves the understanding of the molecular mechanisms involved in the tolerance of plants to salt stress. This work provides a good basis for further functional elucidation of these DEPs using genetic and/or other approaches, and, consequently, candidate genes for genetic engineering to improve crop salt tolerance.

High Throughput Sequencing of Small RNAs in the Two Cucurbita Germplasm with Different Sodium Accumulation Patterns Identifies Novel MicroRNAs Involved in Salt Stress Response.

MicroRNAs (miRNAs), a class of small non-coding RNAs, recognize their mRNA targets based on perfect sequence complementarity. MiRNAs lead to broader changes in gene expression after plants are exposed to stress. High-throughput sequencing is an effective method to identify and profile small RNA populations in non-model plants under salt stresses, significantly improving our knowledge regarding miRNA functions in salt tolerance. Cucurbits are sensitive to soil salinity, and the Cucurbita genus is used as the rootstock of other cucurbits to enhance salt tolerance. Several cucurbit crops have been used for miRNA sequencing but salt stress-related miRNAs in cucurbit species have not been reported. In this study, we subjected two Cucurbita germplasm, namely, N12 (Cucurbita. maxima Duch.) and N15 (Cucurbita. moschata Duch.), with different sodium accumulation patterns, to Illumina sequencing to determine small RNA populations in root tissues after 4 h of salt treatment and control. A total of 21,548,326 and 19,394,108 reads were generated from the control and salt-treated N12 root tissues, respectively. By contrast, 19,108,240 and 20,546,052 reads were obtained from the control and salt-treated N15 root tissues, respectively. Fifty-eight conserved miRNA families and 33 novel miRNAs were identified in the two Cucurbita germplasm. Seven miRNAs (six conserved miRNAs and one novel miRNAs) were up-regulated in salt-treated N12 and N15 samples. Most target genes of differentially expressed novel miRNAs were transcription factors and salt stress-responsive proteins, including dehydration-induced protein, cation/H+ antiporter 18, and CBL-interacting serine/threonine-protein kinase. The differential expression of miRNAs between the two Cucurbita germplasm under salt stress conditions and their target genes demonstrated that novel miRNAs play an important role in the response of the two Cucurbita germplasm to salt stress. The present study initially explored small RNAs in the response of pumpkin to salt stress, and provided valuable information on novel miRNAs and their target genes in Cucurbita.

Proteomic analysis of salt-stress responsive proteins in roots of tomato (Lycopersicon esculentum L.) plants towards silicon efficiency

Salt stress is a rising threat to crop productivity, among several notable consumed crops tomato is often under threat due to salt stress. In this study, the role of Si in restraining salinity stress responses in root proteome and genes involved in stress tolerance has been studied. Fifteen days old tomato (Lycopersicon esculentum L.) plants grown hydroponically with or without NaCl were fed with 2.5 mM Si in the form of potassium silicate [K2SiO3]. The response to a combined effect of NaCl and Si were studied 5 days after treatment. Proteomic analysis indicated that 40 proteins were differentially expressed under Si and/or salt stress treatments. Twenty-four of them were up-regulated by Si supplements (50 mM +NaCl/+Si) and down-regulated in salt-stressed roots (50 mM +NaCl/−Si), and these proteins were mostly associated with stress responses, plant hormones and transcriptional regulations. The rest of them belong to other secondary metabolites. Moreover, 17 differentially expressed proteins (25 mM +NaCl/+Si), up-regulated in the Si treatments, were mostly related to stress responses, plant hormones and cellular biosynthesis, and the rest of the proteins were related to transcriptional regulation, RNA binding and other secondary metabolisms. In addition, 17 protein spots were observed absent in salinity-stressed roots (25/or 50 mM +NaCl/−Si). Moreover, the important genes associated with salt stress responses (leDREB-1, leDREB-2 and leDREB-3), antioxidants (leAPX, leSOD and leCAT genes) and Si transport (leLsi-1, leLsi-2 and leLsi-3) were analyzed by the real-time polymerase chain reaction. The physiological data such as thiobarbituric acid reactive substances, superoxide dismutase as an oxidative stress marker and concentration of Si all correlated well with proteomic and gene expression data. The observed responses to Si supply in salt stressed plants indicate that the Si has a substantial role in alleviating the salinity stress responses by improving the root proteome and activating important genes responsible for stress tolerance.

Comparative proteomic analysis of early salt stress responsive proteins in roots and leaves of rice

Growth and productivity of rice (Oryza sativa L.) are severely affected by salinity. Understanding the mechanisms that protect rice and other important cereal crops from salt stress will help in the development of salt-stress-tolerant strains. In this study, rice seedlings of the same genetic species with various salt tolerances were studied. We first used 2DE to resolve the expressed proteome in rice roots and leaves and then used nanospray liquid chromatography/tandem mass spectrometry to identify the differentially expressed proteins in rice seedlings after salt treatment. The 2DE assays revealed that there were 104 differentially expressed protein spots in rice roots and 59 in leaves. Then, we identified 83 proteins in rice roots and 61 proteins in rice leaves by MS analysis. Functional classification analysis revealed that the differentially expressed proteins from roots could be classified into 18 functional categories while those from leaves could be classified into 11 functional categories. The proteins from rice seedlings that most significantly contributed to a protective effect against increased salinity were cysteine synthase, adenosine triphosphate synthase, quercetin 3-O-methyltransferase 1, and lipoxygenase 2. Further analysis demonstrated that the primary mechanisms underlying the ability of rice seedlings to tolerate salt stress were glycolysis, purine metabolism, and photosynthesis. Thus, we suggest that differentially expressed proteins may serve as marker group for the salt tolerance of rice.

Proteomic analysis of salt-responsive proteins in the leaves of mangrove Kandelia candel during short-term stress.

Salt stress is a major abiotic stress that limits crop productivity in many regions of the world. A comparative proteomic approach to identify salt stress-responsive proteins and to understand the molecular mechanisms was carried out in the woody halophyte Kandelia candel. Four-leaf-old K. candel seedlings were exposed to 150 (control), 300, 450, and 600 mM NaCl for 3 days. Proteins extracted from the leaves of K. candel seedlings were separated by two-dimensional gel electrophoresis (2-DE). More than 900 protein spots were detected on each gel, and 53 differentially expressed protein spots were located with at least two-fold differences in abundance on 2-DE maps, of which 48 were identified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF-TOF/MS). The results showed that K. candel could withstand up to 450 mM NaCl stress by up-regulating proteins that are mainly involved in photosynthesis, respiration and energy metabolism, Na+ compartmentalization, protein folding and assembly, and signal transduction. Physiological data, including superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR) activities, hydrogen peroxide (H2O2) and superoxide anion radicals (O2 −) contents, as well as Na+ content and K+/Na+ ratios all correlated well with our proteomic results. This study provides new global insights into woody halophyte salt stress responses. Identification of differentially expressed proteins promotes better understanding of the molecular basis for salt stress reduction in K. candel.