Osmotic Stress Tolerance Research Articles

Overexpression of an ABA-dependent grapevine bZIP transcription factor, VvABF2, enhances osmotic stress in Arabidopsis.

Overexpression of grapevine VvABF2 gene could enhance osmotic stress tolerance in Arabidopsis thaliana but fully required for ABA signaling. The abscisic acid (ABA)-dependent AREB/ABF-SnRK2 pathway has been demonstrated to play a pivotal role in response to osmotic stress in model plants. However, its function in other specific species, for example grapevine, has not been fully characterized. In this study, grapevine (Vitis vinifera L.) ABSCISIC ACID RESPONSE ELEMENT-BINDING FACTOR2 (VvABF2), a homologous gene of AREB/ABFs form Arabidopsis, was isolated and constitutively expressed in Arabidopsis under the control of the cauliflower mosaic virus 35S promoter. The VvABF2 transgenic Arabidopsis plants showed to be more sensitive to exogenous ABA compared to wild type plants and exhibited significant osmotic tolerance, like polyethylene glycol (PEG) and drought but fully required ABA for signaling. This fact was further confirmed by its downstream gene expression assays. In addition, the determination of ROS antioxidant enzymes (including SOD, POD and CAT) and the MDA of transgenic lines indicated that overexpression of VvABF2 in Arabidopsis significantly increased ROS scavenging ability and thereby reduced the cell membrane damage, which might be ABA-independent. Our results provide evidence that VvABF2 has a similar function to the Arabidopsis homolog in response to osmotic stresses, and that there is a similar ancestral function of this gene in ABA-dependent response to stresses in grapevine.

Overexpression of a protein kinase gene MpSnRK2.10 from Malus prunifolia confers tolerance to drought stress in transgenic Arabidopsis thaliana and apple

Members of the sucrose non-fermenting-1-related protein kinase 2 (SnRK2) family play central roles in the abscisic acid (ABA) signaling pathway and in mediating osmotic stress signaling and tolerance in plants. Previously, 12 full-length coding sequences that belong to SnRK2 gene family were identified and cloned in wild apple species Malus prunifolia. In this study, one of the members, MpSnRK2.10, was overexpressed in Arabidopsis and apple to investigate its potential function in response to drought stress. The results showed that overexpression of this gene did not affect plant growth under normal conditions. However, the transgenic plants showed enhanced tolerance to drought, as indicated by the amelioration in phenotype appearance and physiological indices related to drought stress damage. Additionally, transgenic apple plants overexpressing MpSnRK2.10 exhibited greater sensitivity to ABA compared to wild-type (WT) plants. Moreover, expressions of three stress response genes, MdRAB18, MdRD22, and MdRD29B, were more strongly induced in transgenic apple plants than in the WT when subjected to ABA and mannitol treatments. Taken as a whole, our study suggests that MpSnRK2.10 has a role in the enhancement of ABA signal transduction in response to stress, and that the manipulation of MpSnRK2.10 expression could be a feasible approach for improving abiotic stress tolerance in apple and other important crops.

A cytosolic NAD+-dependent GPDH from maize (ZmGPDH1) is involved in conferring salt and osmotic stress tolerance

BackgroundPlant glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the reduction of dihydroxyacetone phosphate (DHAP) to produce glycerol-3-phosphate (G-3-P), and plays a key role in glycerolipid metabolism as well as stress responses.ResultsIn this study, we report the cloning, enzymatic and physiological characterization of a cytosolic NAD+-dependent GPDH from maize. The prokaryotic expression of ZmGPDH1 in E.coli showed that the enzyme encoded by ZmGPDH1 was capable of catalyzing the reduction of DHAP in the presence of NADH. The functional complementation analysis revealed that ZmGPDH1 was able to restore the production of glycerol-3-phosphate and glycerol in AtGPDHc-deficient mutants. Furthermore, overexpression of ZmGPDH1 remarkably enhanced the tolerance of Arabidopsis to salinity/osmotic stress by enhancing the glycerol production, the antioxidant enzymes activities (SOD, CAT, APX) and by maintaining the cellular redox homeostasis (NADH/NAD+, ASA/DHA, GSH/GSSG). ZmGPDH1 OE Arabidopsis plants also exhibited reduced leaf water loss and stomatal aperture under salt and osmotic stresses. Quantitative real-time RT-PCR analyses revealed that overexpression of ZmGPDH1 promoted the transcripts accumulation of genes involved in cellular redox homeostasis and ROS-scavenging system.ConclusionsTogether, these data suggested that ZmGPDH1 is involved in conferring salinity and osmotic tolerance in Arabidopsis through modulation of glycerol synthesis, stomatal closure, cellular redox and ROS homeostasis.

RNAi mediated silencing of dehydrin gene WZY2 confers osmotic stress intolerance in transgenic wheat.

Dehydrins are involved in the prevention of osmotic damage in plants. Many studies have shown that overexpression of dehydrin genes can enhance the osmotic stress tolerance in transgenic plants. Our previous studies showed a YnSKn-type dehydrin gene WZY2 could be induced by polyethylene glycol (PEG), cold, indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA). In the present study, we examined the phenotype and physiological indices in a dehydrin gene WZY2 RNA interference (RNAi) lines in wheat. Real-time PCR indicated a depressed WZY2 gene expression in transformed wheat. Furthermore, transgenic wheat showed lower relative water content, oxidative-related enzyme activities and higher malondialdehyde (MDA) content than wild-type bread wheat (Zhengyin No.1) under osmotic stress. Overexpression of the WZY2 in Arabidopsis thaliana (L.) Heynh. revealed a significant increase in tolerance to drought stress. Further studies also showed that WZY2 could participate in ABA-induced stomatal closure. These results demonstrated a key function of WZY2 in plant response to osmotic stress.

Time-Course Comparative Metabolite Profiling under Osmotic Stress in Tolerant and Sensitive Tibetan Hulless Barley.

Tibetan hulless barley is widely grown in the extreme environmental conditions of the Qinghai-Tibet Plateau which is characterized by cold, high salinity, and drought. Osmotic stress always occurs simultaneously with drought and its tolerance is a vital part of drought tolerance. The diversity of metabolites leading to osmotic stress tolerance was characterized using widely-targeted metabolomics in tolerant (XL) and sensitive (D) accessions submitted to polyethylene glycol. XL regulated a more diverse set of metabolites than D, which may promote the establishment of a robust system to cope with the stress in XL. Compounds belonging to the group of flavonoids, amino acids, and glycerophospholipids constitute the core metabolome responsive to the stress, despite the tolerance levels. Moreover, 8 h appeared to be a critical time point for stress endurance involving a high accumulation of key metabolites from the class of nucleotide and its derivative which provide the ultimate energy source for the synthesis of functional carbohydrates, lipids, peptides, and secondary metabolites in XL. This intrinsic metabolic adjustment helped XL to efficiently alleviate the stress at the later stages. A total of 22 diverse compounds were constantly and exclusively regulated in XL, representing novel stress tolerance biomarkers which may help improving stress tolerance, especially drought, in hulless barley.

Identification and characterization of the rice pre-harvest sprouting mutants involved in molybdenum cofactor biosynthesis.

In cereal crops, ABA deficiency during seed maturation phase causes pre-harvest sprouting (PHS), and molybdenum cofactor (MoCo) is required for ABA biosynthesis. Here, two rice PHS mutants F254 and F5-1 were characterized. In addition to the PHS, these mutants showed pleiotropic phenotypes such as twisting and slender leaves, and then died when the seedling developed to four or five leaves. Map-based cloning showed that OsCNX6 and OsCNX1 encoding homologs of MoaE and MoeA were responsible for F254 and F5-1 mutants, respectively. Genetic complementation indicated that OsCNX6 not only rescued the PHS and seedling lethal phenotype of the cnx6 mutant, but also recovered the MoCo-dependent enzyme activities such as xanthine dehydrogenase (XDH), aldehyde oxidase (AO), nitrate reductase (NR) and sulfite oxidase (SO). Expression pattern showed that OsCNX6 was richly expressed in seed during embryo maturation by quantitative reverse transcriptase PCR and RNA insitu hybridization. Furthermore, the OsCNX6 overexpression plants can significantly enhance the MoCo-dependent enzyme activities, and improved the osmotic and salt stress tolerance without unfavorable phenotypes. Collectively, these data indicated that OsCNX6 participated in MoCo biosynthesis, and is essential for rice development, especially for seed dormancy and germination, and OsCNX6 could be an effective target for improving abiotic stress tolerance in rice.

BpNAC012 Positively Regulates Abiotic Stress Responses and Secondary Wall Biosynthesis.

NAC (NAM, ATAF1/2, and CUC2) transcription factors play important roles in plant biological processes and stress responses. Here, we characterized the functional roles of BpNAC012 in white birch (Betula platyphylla). We found that BpNAC012 serves as a transcriptional activator. Gain- and loss-of-function analyses revealed that the transcript level of BpNAC012 was positively associated with salt and osmotic stress tolerance. BpNAC012 activated the core sequence CGT[G/A] to induce the expression of abiotic stress-responsive downstream genes, including Δ-1-pyrroline-5-carboxylate synthetase, superoxide dismutase, and peroxidase, resulting in enhanced salt and osmotic stress tolerance in BpNAC012 overexpression transgenic birch lines. We also showed that BpNAC012 is expressed predominantly in mature stems and that RNA interference-induced suppression of BpNAC012 caused a drastic reduction in the secondary wall thickening of stem fibers. Overexpression of BpNAC012 activated the expression of secondary wall-associated downstream genes by directly binding to the secondary wall NAC-binding element sites, resulting in ectopic secondary wall deposition in the stem epidermis. Moreover, salt and osmotic stresses elicited higher expression levels of lignin biosynthetic genes and elevated lignin accumulation in BpNAC012 overexpression lines. These findings provide insight into the functions of NAC transcription factors.

Comparison of changes in water status and photosynthetic parameters in wild type and abscisic acid-deficient sitiens mutant of tomato (Solanum lycopersicum cv. Rheinlands Ruhm) exposed to sublethal and lethal salt stress

Abscisic acid (ABA) regulates many salt stress-related processes of plants such as water balance, osmotic stress tolerance and photosynthesis. In this study we investigated the responses of wild type (WT) and the ABA-deficient sitiens mutant of tomato (Solanum lycopersicum cv. Rheinlands Ruhm) to sublethal and lethal salt stress elicited by 100 mM and 250 mM NaCl, respectively. Sitiens mutants displayed much higher decrease in water potential, stomatal conductance and net CO2 assimilation rate under high salinity, especially at lethal salt stress, than the WT. However, ABA deficiency in sitiens caused more severe osmotic stress and more moderate ionic stress, higher K+/Na+ ratio, in leaf tissues of plants exposed to salt stress. The higher salt concentration caused irreversible damage to Photosystem II (PSII) reaction centres, severe reduction in the linear photosynthetic electron transport rate and in the effective quantum yields of PSII and PSI in sitiens plants. The cyclic electron transport (CET) around PSI, which is an effective defence mechanism against the damage caused by photoinhibition in PSI, decreased in sitiens mutants, while WT plants were able to increase CET under salt stress. This suggests that the activation of CET needs active ABA synthesis and/or signalling. In spite of ABA deficiency, proline accumulation could alleviate the stress injury at sublethal salt stress in the mutants but its accumulation was not sufficient at lethal salt stress.

Identification, Classification, and Functional Analysis of AP2/ERF Family Genes in the Desert Moss Bryum argenteum.

Bryum argenteum is a desert moss which shows tolerance to the desert environment and is emerging as a good plant material for identification of stress-related genes. AP2/ERF transcription factor family plays important roles in plant responses to biotic and abiotic stresses. AP2/ERF genes have been identified and extensively studied in many plants, while they are rarely studied in moss. In the present study, we identified 83 AP2/ERF genes based on the comprehensive dehydrationrehydration transcriptomic atlas of B. argenteum. BaAP2/ERF genes can be classified into five families, including 11 AP2s, 43 DREBs, 26 ERFs, 1 RAV, and 2 Soloists. RNA-seq data showed that 83 BaAP2/ERFs exhibited elevated transcript abundances during dehydration–rehydration process. We used RT-qPCR to validate the expression profiles of 12 representative BaAP2/ERFs and confirmed the expression trends using RNA-seq data. Eight out of 12 BaAP2/ERFs demonstrated transactivation activities. Seven BaAP2/ERFs enhanced salt and osmotic stress tolerances of yeast. This is the first study to provide detailed information on the identification, classification, and functional analysis of the AP2/ERFs in B. argenteum. This study will lay the foundation for the further functional analysis of these genes in plants, as well as provide greater insights into the molecular mechanisms of abiotic stress tolerance of B. argenteum.

Enhanced Drought and Osmotic Stress Tolerance in Transgenic Potato Plants Expressing AtCDPK1, a Calcium-Dependent Protein Kinase

Growing evidence indicates that calcium-dependent protein kinases (CDPKs) are involved in many aspects of plant’s growth, development and responses to biotic and abiotic stresses. Previous researchers reported AtCDPK1 gene used as a positive regulator in salt and drought stress signaling. This study aimed to increase transgenic potatoes’ (Solanum tuberosum L. cv. Favorita) tolerance to the drought and osmotic stresses. Transgenic potato plants expressing AtCDPK1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter (referred to as T-plants) were successfully generated through Agrobacterium-mediated transformation. Two representative transgenic T6 and T25 lines were evaluated for enhanced tolerance to drought and osmotic stresses. The survival rates of transgenic lines T6 and T25 (67 and 54%, respectively) were higher than that of wild type (WT) plants (25%) after the drought stress. After 15 days of PEG stress, the survival rate of T6 was 45.68%, whereas that of the WT line was approximately 20%. The survival rate of transgenic lines was very higher than that of WT after 15 days of PEG stress. The content of proline and malondialdehyde (MDA) were clear difference between control and transgenic lines after the drought and osmotic stresses. After the 24 h osmotic treatment, content of proline in transgenic plants was very higher than that of the control, enhanced 26%, reached an extremely significant level (P < 0.05). MDA content in transgenic plants was lower than the control in the same period, while the biggest difference appeared at 24 h (P < 0.05), and MDA content of transgenic plants reduced 28% than the control. qRT-PCR proves that relative expressions of StP5CS and StProDH genes in the transgenic lines both increased in early period, and then decreased after PEG 6000 stress. These results suggested that enhanced AtCDPK1 expression affected the transcription of stress-associated genes and the content of proline and MDA in transgenic plants, which leads to improved tolerance ability in transgenic potatoes.

Poly-β-hydroxybutyrate (PHB)-accumulating Halomonas improves the survival, growth, robustness and modifies the gut microbial composition of Litopenaeus vannamei postlarvae

The PHB-accumulating Halomonas strain was isolated from local solar saltworks and was cultured in CM culture medium with addition of 30 g L−1 glucose to favor the PHB accumulation in the cells. The effect of Halomonas-PHB on the survival, growth, osmotic stress tolerance, resistance against Vibrio anguillarum challenge and the gut microbial composition of Litopenaeus vannamei postlarvae were investigated. The postlarvae PL6 were fed Artemia nauplii enriched with Halomonas-PHB (HM.PHB), Halomonas without PHB accumulation (HM), commercial PHB particles (par.PHB) and non-enriched Artemia nauplii (Control), respectively, for two weeks. The results revealed that both Halomonas-PHB and particle PHB could improve the survival, growth, and enhance the robustness of the shrimp PLs under both challenge and non-challenged conditions. High throughput sequencing on gut microbiota indicated that Halomonas-PHB not only suppressed the propagation of Vibrio, but also diverged to gut microbiota towards to the probiotic bacteria propagation (i.e. Bacillus and Lactobacillus) in the gut. In conclusion, the Halomonas-PHB is more efficient than particle PHB in L. vannamei larviculture and thus can be applied as feed additive in shrimp culture.

Regulatory Role of Silicon in Mediating Differential Stress Tolerance Responses in Two Contrasting Tomato Genotypes Under Osmotic Stress.

Previous studies have shown the role of silicon (Si) in mitigating the adverse effect of drought stress in different crop species. However, data are lacking on a comparison of drought tolerant and drought sensitive crop cultivars in response to Si nutrition. Therefore, the aim of this study was to elucidate the mechanism (s) by which two contrasting tomato genotypes respond to Si nutrition under osmotic stress condition. Two tomato lines contrasting in their response to drought stress were hydroponically grown under polyethylene glycol (PEG, 6000) and two regimes of Si (0 and 1.5 mM). Metabolite profiling was performed in two lines. Growth and relevant physiological parameters, and expression levels of selected genes were also measured. Si application resulted in improved osmotic stress tolerance in both drought tolerant line LA0147 and drought sensitive line FERUM. In the drought tolerant line, Si enhanced uptake of sulfur (S) and ammonium () which led to a significantly higher production of amino acids arginine, methionine, serine, and glycine. While in the drought sensitive line, Si significantly increased production of amino acids proline and GABA which further lowered the level of GSSG to GSH ratio and thus balanced the redox homeostasis under osmotic stress. The higher significant production of amino acids arginine, methionine, GABA, and proline enhanced production of free polyamines putrescine and spermidine and improved osmotic stress tolerance. Therefore, we conclude that Si distinctively regulated osmotic stress tolerance in two contrasting tomato genotypes by differential accumulation of relevant amino acids which eventually led to enhanced polyamine metabolism.

Isolation and identification of Ammodendron bifolium endophytic bacteria and the action mechanism of selected isolates-induced seed germination and their effects on host osmotic-stress tolerance.

This study aimed to identify Ammodendron bifolium endophytic bacteria, and to evaluate promoting mechanism of selected isolates on seed germination and their effects on host osmotic-stress tolerance. Forty-five strains were isolated from A. bifolium and were classified into 13 different genera by 16S rDNA gene sequence analysis. AY3, AY9 and AG18, which were identified as Staphylococcus, Kocuria, Bacillus sp., promoted host seed ethylene release during germination. Ethrel and 1-aminocyclopropane-1-carboxylic acid (ACC) imitated the effect of AY3, AY9 and AG18 on seed germination. The data suggest that ethylene mediates AY3-, AY9-, AG18-induced A. bifolium seed germination. In addition, osmotic stress prevented seed germination and radicle elongation. However, the inhibitory effect of osmotic stress on seed germination and radicle elongation were rescued by AY3, AY9 and AG18. The results show that AY3, AY9 and AG18 increased osmotic-stress tolerance in A. bifolium. AY3, AY9, AG18 induced A. bifolium seed germination through promoting ethylene production during endophytic bacteria-plant interaction, and increase osmotic-stress tolerance in A. bifolium. AY3, AY9 and AG18 are potential candidates for the protection of A. bifolium.

Screening and Evaluation of Saline–Alkaline Tolerant Germplasm of Rice (Oryza sativa L.) in Soda Saline–Alkali Soil

The improvement and development of saline–alkali land is of great significance for promoting food production and sustainable development. It is necessary to study the mechanism of saline–alkaline tolerance and breed saline–alkaline tolerant crops to improve the utilization of saline–alkali land. For this study, we conducted a three-year pot experiment to screen the saline–alkaline tolerant germplasm of 72 rice genotypes from hundreds of elite cultivars during the whole growth period using a certain proportion of soda saline–alkali soil. The selected salt-tolerant variety was combined with a salt-sensitive variety to analyze the saline–alkaline tolerance mechanism by using the saline–alkaline soil leachate. We eliminated 36 genotypes with low seedling survival rates under salt–alkali stress, and the salt-tolerant Jiudao-66 (D68) variety had a higher survival rate than most varieties. The membership degree of Jiudao-66, according to the salt tolerance index of multiple agronomic traits, is higher than that of 34 varieties, with a higher survival rate except when compared to D36. The survival rate and these salt tolerance indexes of Jiudao-66 were significantly higher than those of Kitaake (salt-sensitive). Under the stress of leachate, the content of proline and soluble sugars in the shoots of Jiudao-66 were higher than that of Kitaake, and the total antioxidant capacity was stronger than that of Kitaake. However, the content of malondialdehyde was lower than that of Kitaake. Additionally, the Na+/K+ ratios in shoots and roots were not significantly differently between Kitaake and Jiudao-66. The results showed that Jiudao-66, as a salt-tolerant variety, is more tolerant to salt and alkali in a near-natural state due to its stronger tolerance of osmotic stress, and it can accumulate more proline and soluble sugars under stress. At the same time, Jiudao-66 also has a stronger antioxidant capacity. Its ion regulation ability has no obvious advantage.

Nitric oxide contributes to methane-induced osmotic stress tolerance in mung bean

BackgroundOsmotic stress is a major abiotic stress limiting crop production by affecting plant growth and development. Although previous reports discovered that methane (CH4) has a beneficial effect on osmotic stress, the corresponding downstream signal(s) is still elusive.ResultsPolyethylene glycol (PEG) treatment progressively stimulated the production of CH4 in germinating mung bean seeds. Exogenous CH4 and sodium nitroprusside (SNP) not only triggered nitric oxide (NO) production in PEG-stressed plants, but also alleviated the inhibition of seed germination. Meanwhile, amylase activity was activated, thus accelerating the formation of reducing sugar and total soluble sugar. Above responses could be impaired by NO scavenger(s), suggesting that CH4-induced stress tolerance was dependent on NO. Subsequent tests showed that CH4 could reestablish redox balance in a NO-dependent fashion. The addition of inhibitors of the nitrate reductase (NR) and NO synthase in mammalian (NOS), suggested that NR and NOS-like protein might be partially involved in CH4-alleviated seed germination inhibition. In vitro and scavenger tests showed that NO-mediated S-nitrosylation might be associated with above CH4 responses.ConclusionsTogether, these results indicated an important role of endogenous NO in CH4-enhanced plant tolerance against osmotic stress, and NO-regulated redox homeostasis and S-nitrosylation might be involved in above CH4 action.

Stress-induced expression of the sweetpotato gene IbLEA14 in poplar confers enhanced tolerance to multiple abiotic stresses

Late embryogenesis abundant (LEA) proteins are small, highly hydrophilic proteins that act as protectors of macromolecules and increase abiotic stress tolerance in plants. We previously reported that overexpressing sweetpotato IbLEA14 under the control of the CaMV 35S promoter increased osmotic and salt stress tolerance in transgenic sweetpotato calli. In this study, we generated transgenic poplar plants (Populus alba × P. glandulosa) expressing IbLEA14 under the control of the oxidative stress-inducible SWPA2 promoter (referred to as SL plants). Among the 15 SL plants obtained, three lines (SL2, SL7, and SL12) were established based on IbLEA14 transcript levels, tolerance to salt stress and Southern blot analysis. The SL plants exhibited less damage in response to methyl viologen-mediated oxidative stress than non-transgenic (NT) plants. SL plants also showed enhanced tolerance to drought, salt, and heat stress, which was associated with higher photosystem II efficiency and lower malondialdehyde levels compared with NT plants. Furthermore, SL plants had higher levels of monolignol biosynthesis-related gene transcripts under drought stress compared with NT plants. Finally, SL plants exhibited increased tolerance to heat stress, which is associated with the high thermostability of IbLEA14 protein. SL plants might be useful for reforestation on global marginal lands, including desertification and reclaimed areas.

Levansucrase from Halomonas smyrnensis AAD6T: first halophilic GH-J clan enzyme recombinantly expressed, purified, and characterized

Fructans, homopolymers of fructose produced by fructosyltransferases (FTs), are emerging as intriguing components in halophiles since they are thought to be associated with osmotic stress tolerance and overall fitness of microorganisms and plants under high-salinity conditions. Here, we report on the full characterization of the first halophilic FT, a levansucrase from Halomonas smyrnensis AAD6T (HsLsc; EC 2.4.1.10). The encoding gene (lsc) was cloned into a vector with a 6xHis Tag at its C-terminus, then expressed in Escherichia coli. The purified recombinant enzyme (47.3kDa) produces levan and a wide variety of fructooligosaccharides from sucrose, but only in the presence of high salt concentrations (> 1.5M NaCl). HsLsc showed Hill kinetics and pH and temperature optima of 5.9 and 37°C, respectively. Interestingly, HsLsc was still very active at salt concentrations close to saturation (4.5M NaCl) and was selectively inhibited by divalent cations. The enzyme showed high potential in producing novel saccharides derived from raffinose as both fructosyl donor and acceptor and cellobiose, lactose, galactose, and ʟ-arabinose as fructosyl acceptors. With its unique biochemical characteristics, HsLsc is an important enzyme for future research and potential industrial applications in a world faced with drought and diminishing freshwater supplies.

Transcriptional regulation of osmotic stress tolerance in wheat (Triticum aestivum L.).

The current review provides an updated, new insights into the regulation of transcription mediated underlying mechanisms of wheat plants to osmotic stress perturbations. Osmotic stress tolerance mechanisms being complex are governed by multiple factors at physiological, biochemical and at the molecular level, hence approaches like "OMICS" that can underpin mechanisms behind osmotic tolerance in wheat is of paramount importance. The transcription factors (TFs) are a class of molecular proteins, which are involved in regulation, modulation and orchestrating the responses of plants to a variety of environmental stresses. Recent reports have provided novel insights on the role of TFs in osmotic stress tolerance via direct molecular links. However, our knowledge on the regulatory role TFs during osmotic stress tolerance in wheat remains limited. The present review in its first part sheds light on the importance of studying the role of osmotic stress tolerance in wheat plants and second aims to decipher molecular mechanisms of TFs belonging to several classes, including DREB, NAC, MYB, WRKY and bHLH, which have been reported to engage in osmotic stress mediated gene expression in wheat and third part covers the systems biology approaches to understand the transcriptional regulation of osmotic stress and the role of long non-coding RNAs in response to osmotic stress with special emphasis on wheat. The current concept may lead to an understanding in molecular regulation and signalling interaction of TFs under osmotic stress to clarify challenges and problems for devising potential strategies to improve complex regulatory events involved in plant tolerance to osmotic stress adaptive pathways in wheat.

Characterization of TaDREB1 in wheat genotypes with different seed germination under osmotic stress

BackgroundThe cis-acting element DRE/CRT plays an important role in activating gene expression responsive to osmotic stress, low temperature and high-salinity. DREB1/CBF genes encode DRE-binding proteins with the function as transcript activators. TaDREB1 was also found to be induced by osmotic stress.MethodsThe dates of osmotic stress was assessed by seed germination drought resistance index; the full-length cDNA sequences of TaDREB1 gene were downloaded from NCBI datebase; identification of allelic variation and transcript expression were assessed by PCR and semi-quantitive RT-PCR analysis, respectively.ResultsTotal 13 new allele variations of TaDREB1 were identified in the germplasms tested in the paper, including 5 TaDREB1-A on chromosome 3AL, 4 TaDREB1-B on chromosome 3BL and 4 TaDREB1-D on chromosome 3DL. In each variety, there existed two loci of TaDREB1-D genes, named TaDREB1-D1 and TaDREB1-D2, both of which had the similar nucleotide sequence except an 11 bp insertion in the former. In wheat seeds under osmotic stress, we did not detect the transcript expression level of TaDREB1-A and TaDREB1-B, but that of TaDREB1-D.ConclusionsThe capacity of osmotic stress tolerance was closely correlated with the expression level and tendency of TaDREB1-D.

Osmoregulation in decapod crustaceans: physiological and genomic perspectives

A central question in evolutionary biology represents understanding the molecular basis of adaptive response to differing environmental salinity gradients. The capacity to osmoregulate is considered to be the principal function through which adaptation occurs in different or fluctuating osmotic niches. Decapod crustaceans represent an interesting research group for exploring the underlying genetic/genomic mechanisms involved with this process. The genomic basis of osmoregulation involves modifying expression patterns of candidate genes for ionic balance for short-/long-term acclimation to salinity change while long-term persistence in the altered salinity conditions can facilitate adaptation via novel mutations over an evolutionary time frame. So far, 32 candidate genes have been identified that have important functional roles in maintaining ionic balance across decapod crustacean lineages. Certain genes are considered to play principal/vital roles while others apparently have secondary or minor roles. This group of genes falls under several broad biological categories including: sensing osmotic stress, signal transduction, activating candidate genes, osmotic stress tolerance, ion transportation, active ion exchange, and regulation of cell volume. Most studies conducted to date have focused only on a few principal genes to better understand osmoregulatory processes, while minor role-playing genes remained largely unexplored. The information available currently reviewed here can provide important clues to decipher the molecular mechanisms involved with osmoregulation broadly across crustacean lineages.