Role In Abiotic Stress Tolerance Research Articles

PgPAP18, a heat-inducible novel purple acid phosphatase 18-like gene (PgPAP18-like) from Pennisetum glaucum, may play a crucial role in environmental stress adaptation

Purple acid phosphatases (PAPs) are ubiquitously present in plants, but their functional roles are still elusive. In this study, we isolated a novel full-length Pennisetum glaucum purple acid phosphatase 18-like (PgPAP18-like) gene, from pearl millet. PgPAP18 cDNA comprises 1410 bp and it encodes 469 amino acids including signal peptide. Insilico analysis of PgPAP18 emphasized that it belongs to metallo-phosphatase superfamily with di-nuclear (Fe-Zn) metal center. The gene further cloned into pET-28a (+) vector for protein expression and the purified recombinant protein showed phosphatase activity with para nitro phenyl phosphate (102 U mg−1). SDS-PAGE analysis revealed its molecular size of approximately 52.5 kDa and estimated isoelectric point (PI) as 6.21. The functional role of PgPAP18 in Escherichia coli augments the tolerance against (10%) of heat, (9%) of salt, (8.5%) of PEG, and (7%) of (CuSO4). pPICZ A-PAP18 recombinant clone expressed yeast cells were also affirmed E. coli stress tolerance. Spatial and temporal expression of Pennisetum leaf PAP18 transcript was significantly accumulated after 24 h of heat induction. The substantial changing expression level of PgPAP18 under heat treatment suggested that PgPAP18 may play crucial role in the accumulation of PAP18 under heat stress. Results indicated that PgPAP18 may play defensive role against environmental stresses and confer stress adaptation to the stress-tolerant plant. To the best of our best knowledge, the PgPAP18 gene isolation and recombinant protein purification from Pennisetum are first time described here which may play a critical role in abiotic stress tolerance in addition to phosphatase activity.

Molecular Characterization of a MYB Protein from Oryza sativa for its Role in Abiotic Stress Tolerance

ABSTRACT The MYB family represents one of the most abundant classes of transcriptional regulators that perform pivotal role under different developmental processes and abiotic stresses. In present study, a MYB gene from Oryza sativa was selected for functional characterization. Bioinformatics analysis revealed that OsMYB1 cDNA encodes R2-R3 type DNA binding domain consisting of 413 amino acids having size of 44 kDa and pI of 6.24. DNA binding domain containing region was cloned and over-expressed in E. coli. Then, the survival of pGEX-OsMYB1 transformed E. coli cells was compared with control plasmid under different concentrations of NaCl, mannitol, high and low temperature. pGEX-OsMYB1 enhanced the survival of cells at high temperature and salinity. Electrophoretic mobility shift assays (EMSAs) have shown that recombinant OsMYB1 protein was able to bind with DIG labeled probe containing MYB binding site. RT-qPCR analysis revealed high MYB1 expression under wounding, salt, drought and heat stresses in rice. Expression was 23 fold higher in response to wounding demonstrating the worth of OsMYB1 up-regulation in wounding. Intrinsic disorder profile predicted that OsMYB1 exhibits 60% degree of intrinsic disorder proposing that these regions might be involved in DNA binding specificity and protein-protein interaction. The positive response of OsMYB1 suggests that its over-expression in crop plants may help in providing protection to plants to grow under abiotic stresses.

Molecular Characterization of Barley Methionine γ-Lyase and Gene Expression by Abiotic Stress and Aspartate Family Amino Acids

The concentrations of free proline, leucine, and isoleucine increase significantly in plant cells under osmotic stress. Methionine γ-lyase (MGL) catalyzes methionine to produce α-ketobutyrate, which is a precursor for isoleucine biosynthesis. Arabidopsis MGL gene is induced by drought and salt stresses, suggesting that plant MGL plays a role in isoleucine biosynthesis for abiotic stress tolerance in plants. However, enzymatic characterization and gene expression of plant MGL are described mostly based on results of Arabidopsis MGL. This study identified putative MGL genes from barley and some monocot plants that encode amino acid sequences showing homology with that of Arabidopsis MGL. Plant MGLs were distinguishable between monocots and dicots from their gene and amino acid sequences. Barley MGL catalyzed α, γ-elimination reaction more than α, β-elimination reaction, as did Arabidopsis MGL. Barley MGL gene was up-regulated considerably by drought stress, but down-regulated by the aspartate family amino acids, cystathionine, homocysteine, methionine, threonine, and isoleucine, with especially considerable reduction by methionine. These results suggest that barley MGL gene should be induced by drought stress specifically and be reduced by methionine to reserve methionine for the production of S-adenosylmethionine and the following metabolites, which are precursors for ethylene and polyamines playing a role in abiotic stress tolerance.

Involvement of glyoxalases and glutathione reductase in conferring abiotic stress tolerance to Jatropha curcas L.

In the current study, we characterized three crucial enzymes, glyoxalase I, II (JcGLYI, JcGLYII) and glutathione reductase (JcGR) that are known to play key role in metabolite degradation and oxidative stress tolerance. Methylglyoxal (MG) produced during abiotic stress causes severe damage to plants and glyoxalases along with glutathione (GSH) detoxify MG to non-toxic compounds. Our transcriptome analysis of Jatropha revealed the presence of putative JcGLYI, JcGLYII and JcGR. The Conserved Domain Database (CDD) analysis of JcGLYI showed two active sites for metal and glutathione binding while JcGLYII had β-lactamase domain. The three corresponding genes were heterologously expressed in E.coli BL-21(DE3) individually and the purified proteins were analysed through MALDI-TOF analysis. JcGLYI, II and JcGR showed specific activity of 1.08, 0.913 and 0.12mmolmin−1mg−1 protein with hemithioacetal, S-d-lactoyl glutathione (SLG) and oxidised glutathione (GSSG) as substrates respectively. JcGLYI sequence alignment, phylogenetic analysis together with its enzyme kinetics indicated its Ni2+ specificity. Bacterial and yeast growth curves confirmed their protective role against PEG (5%), NaCl (200mM) and MG (5mM). The mRNA expression levels and enzyme activities of these three important enzymes in leaves and roots under drought, salt and combined stress conditions along with total glutathione content were assessed. Our results clearly demonstrated the expression and activities of GLYI and GLYII in corroboration with GR under the drought and salt stress which actively metabolised harmful MG into less toxic compounds, suggesting their protective role in abiotic stress tolerance in J. curcas.

Identification and characterization of two faba bean (Vicia faba L.) WRKY transcription factors and their expression analysis during salt and drought stress

SUMMARYDrought and salinity are two major environmental factors limiting faba bean growth, leading to considerable reduction in their productivity. The WRKY gene family act as major transcription factors that might play an important role in abiotic stress tolerance. In the present study, two partial sequences sharing significant homology with known WRKY genes were isolated from faba bean by polymerase chain reaction (PCR) amplification using degenerate primers targeting the well-conserved WRKY domain. The isolated WRKY gene fragments were designated as VfWRKY1 and VfWRKY2 showing 62% similarity between them. Sequence and phylogenetic analyses revealed that VfWRKY1 and VfWRKY2 belong to WRKY group I and could be grouped with their orthologues from other plant species. The gene expression profile of VfWRKY1 and VfWRKY2 in faba bean showed that they are significantly accumulated in various plant organs. Further, quantitative real-time PCR analysis showed that both transcripts were responsive to drought and salt stress, and also they are genotype dependent, meaning that different faba bean cultivars respond in a different way to drought and salt challenge. The expression patterns obtained suggest the important roles of VfWRKY1 and VfWRKY2 in drought and salt stress response and tolerance. This knowledge might be helpful in the identification of drought-tolerant cultivars and provide potential candidate markers for faba bean breeding in order to develop osmotic-stress-tolerant cultivars.

Soybean TIP Gene Family Analysis and Characterization of GmTIP1;5 and GmTIP2;5 Water Transport Activity.

Soybean, one of the most important crops worldwide, is severely affected by abiotic stress. Drought and flooding are the major abiotic stresses impacting soybean yield. In this regard, understanding water uptake by plants, its utilization and transport has great importance. In plants, water transport is mainly governed by channel forming aquaporin proteins (AQPs). Tonoplast intrinsic proteins (TIPs) belong to the plant-specific AQP subfamily and are known to have a role in abiotic stress tolerance. In this study, 23 soybean TIP genes were identified based on the latest soybean genome annotation. TIPs were characterized based on conserved structural features and phylogenetic distribution. Expression analysis of soybean TIP genes in various tissues and under abiotic stress conditions demonstrated tissue/stress-response specific differential expression. The natural variations for TIP genes were analyzed using whole genome re-sequencing data available for a set of 106 diverse soybean genotypes including wild types, landraces and elite lines. Results revealed 81 single-nucleotide polymorphisms (SNPs) and several large insertions/deletions in the coding region of TIPs. Among these, non-synonymous SNPs are most likely to have a greater impact on protein function and are candidates for molecular studies as well as for the development of functional markers to assist breeding. The solute transport function of two TIPs was further validated by expression in Xenopus laevis oocytes. GmTIP1;5 was shown to facilitate the rapid movement of water across the oocyte membrane, while GmTIP2;5 facilitated the movement of water and boric acid. The present study provides an initial insight into the possible roles of soybean TIP genes under abiotic stress conditions. Our results will facilitate elucidation of their precise functions during abiotic stress responses and plant development, and will provide potential breeding targets for modifying water movement in soybean.

Genome-wide identification, characterization and expression profiling of LIM family genes in Solanum lycopersicum L.

LIM domain proteins, some of which have been shown to be actin binding proteins, are involved in various developmental activities and cellular processes in plants. To date, the molecular defense-related functions of LIM family genes have not been investigated in any solanaceous vegetable crop species. In this study, we identified 15 LIM family genes in tomato (Solanum lycopersicum L.) through genome-wide analysis and performed expression profiling in different organs of tomato, including fruits at six different developmental stages. We also performed expression profiling of selected tomato LIM genes in plants under ABA, drought, cold, NaCl and heat stress treatment. The encoded proteins of the 15 tomato LIM genes were classified into two main groups, i.e., proteins similar to cysteine-rich proteins and plant-specific DAR proteins, based on differences in functional domains and variability in their C-terminal regions. The DAR proteins contain a so far poorly characterized zinc-finger-like motif that we propose to call DAR-ZF. Six of the 15 LIM genes were expressed only in flowers, indicating that they play flower-specific roles in plants. The other nine genes were expressed in all organs and at various stages of fruit development. SlβLIM1b was expressed relatively highly at the later stage of fruit development, but three other genes, SlWLIM2a, SlDAR2 and SlDAR4, were expressed at the early stage of fruit development. Seven genes were induced by ABA, five by cold, seven by drought, eight by NaCl and seven by heat treatment respectively, indicating their possible roles in abiotic stress tolerance. Our results will be useful for functional analysis of LIM genes during fruit development in tomato plants under different abiotic stresses.

HyPRP1 Gene Suppressed by Multiple Stresses Plays a Negative Role in Abiotic Stress Tolerance in Tomato

Many hybrid proline-rich protein (HyPRP) genes respond to biotic and abiotic stresses in plants, but little is known about their roles other than as putative cell-wall structural proteins. A HyPRP1 gene encodes a protein with proline-rich domain, and an eight-cysteine motif was identified from our previous microarray experiments on drought-tolerant tomato. In this study, the expression of the HyPRP1 gene in tomato was suppressed under various abiotic stresses, such as drought, high salinity, cold, heat, and oxidative stress. Transgenic functional analysis showed no obvious changes in phenotypes, but enhanced tolerance to various abiotic stresses (e.g., oxidative stress, dehydration, and salinity) was observed in RNAi transgenic plants. Interestingly, several SO2 detoxification-related enzymes, including sulfite oxidase, ferredoxins (Fds), and methionine sulfoxide reductase A (Msr A), were revealed in HyPRP1-interacting proteins identified by Yeast Two-Hybrid screening. More sulfates and transcripts of Msr A and Fds were accumulated in HyPRP1 knockdown lines when wild-type plants were exposed to SO2 gas. Our findings illustrate that the tomato HyPRP1 is a negative regulator of salt and oxidative stresses and is probably involved in sulfite metabolism.

Multifunctional biomolecules with roles in abiotic stress tolerance as well as nutraceutical potential

Environmental challenges such as soil salinity and drought are serious threats to global food security and biodiversity, making the selection or development of stress-tolerant genotypes of crops and native plants necessary. Certain biochemical compounds synthesized by plants are directly involved in ameliorating the effects of environmental stress in characteristic ways. Further, the biochemical composition of edible parts of crops is directly related to human health, deficiencies of certain nutrients being associated with major health conditions and healthcare costs, and public awareness of functional foods also increasing. Interestingly, the unique biochemical properties of some biomolecules involved in plant stress tolerance are also associated with significant roles in human metabolism and health. This work summarises the biochemical properties and functions of four selected biomolecules with such dual significance, i.e., abscisic acid (a key hormone with roles in plant development and abiotic stress response), glycine betaine (a quaternary ammonium compound which functions as an osmoprotectant), vitamin E components (antioxidants), and phenolic compounds (antioxidants), all four also having significant nutraceutical effects.

Accumulation of Flavonols over Hydroxycinnamic Acids Favors Oxidative Damage Protection under Abiotic Stress.

Efficient detoxification of reactive oxygen species (ROS) is thought to play a key role in enhancing the tolerance of plants to abiotic stresses. Although multiple pathways, enzymes, and antioxidants are present in plants, their exact roles during different stress responses remain unclear. Here, we report on the characterization of the different antioxidant mechanisms of tomato plants subjected to heat stress, salinity stress, or a combination of both stresses. All the treatments applied induced an increase of oxidative stress, with the salinity treatment being the most aggressive, resulting in plants with the lowest biomass, and the highest levels of H2O2 accumulation, lipid peroxidation, and protein oxidation. However, the results obtained from the transcript expression study and enzymatic activities related to the ascorbate-glutathione pathway did not fully explain the differences in the oxidative damage observed between salinity and the combination of salinity and heat. An exhaustive metabolomics study revealed the differential accumulation of phenolic compounds depending on the type of abiotic stress applied. An analysis at gene and enzyme levels of the phenylpropanoid metabolism concluded that under conditions where flavonols accumulated to a greater degree as compared to hydroxycinnamic acids, the oxidative damage was lower, highlighting the importance of flavonols as powerful antioxidants, and their role in abiotic stress tolerance.

Over-expression of a NAC 67 transcription factor from finger millet (Eleusine coracana L.) confers tolerance against salinity and drought stress in rice.

BackgroundNAC proteins (NAM (No apical meristem), ATAF (Arabidopsis transcription activation factor) and CUC (cup-shaped cotyledon)) are plant-specific transcription factors reported to be involved in regulating growth, development and stress responses. Salinity responsive transcriptome profiling in a set of contrasting finger millet genotypes through RNA-sequencing resulted in the identification of a NAC homolog (EcNAC 67) exhibiting differential salinity responsive expression pattern.MethodsFull length cDNA of EcNAC67 was isolated, characterized and validated for its role in abiotic stress tolerance through agrobacterium mediated genetic transformation in a rice cultivar ASD16.ResultsBioinformatics analysis of putative NAC transcription factor (TF) isolated from a salinity tolerant finger millet showed its genetic relatedness to NAC67 family TFs in related cereals. Putative transgenic lines of rice over-expressing EcNAC67 were generated through Agrobacterium mediated transformation and presence/integration of transgene was confirmed through PCR and southern hybridization analysis. Transgenic rice plants harboring EcNAC67 showed enhanced tolerance against drought and salinity under greenhouse conditions. Transgenic rice plants were found to possess higher root and shoot biomass during stress and showed better revival ability upon relief from salinity stress. Upon drought stress, transgenic lines were found to maintain higher relative water content and lesser reduction in grain yield when compared to non-transgenic ASD16 plants. Drought induced spikelet sterility was found to be much lower in the transgenic lines than the non-transgenic ASD16.ConclusionResults revealed the significant role of EcNAC67 in modulating responses against dehydration stress in rice. No detectable abnormalities in the phenotypic traits were observed in the transgenic plants under normal growth conditions. Results indicate that EcNAC67 can be used as a novel source for engineering tolerance against drought and salinity stress in rice and other crop plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-016-0261-1) contains supplementary material, which is available to authorized users.

PtrA/NINV, an alkaline/neutral invertase gene of Poncirus trifoliata, confers enhanced tolerance to multiple abiotic stresses by modulating ROS levels and maintaining photosynthetic efficiency.

BackgroundAlkaline/neutral invertase (A/N-INV), an enzyme that hydrolyzes sucrose irreversibly into glucose and fructose, is essential for normal plant growth,development, and stress tolerance. However, the physiological and/or molecular mechanism underpinning the role of A/N-INV in abiotic stress tolerance is poorly understood.ResultsIn this report, an A/N-INV gene (PtrA/NINV) was isolated from Poncirus trifoliata, a cold-hardy relative of citrus, and functionally characterized. PtrA/NINV expression levels were induced by cold, salt, dehydration, sucrose, and ABA, but decreased by glucose. PtrA/NINV was found to localize in both chloroplasts and mitochondria. Overexpression of PtrA/NINV conferred enhanced tolerance to multiple stresses, including cold, high salinity, and drought, as supported by lower levels of reactive oxygen species (ROS), reduced oxidative damages, decreased water loss rate, and increased photosynthesis efficiency, relative to wild-type (WT). The transgenic plants exhibited higher A/N-INV activity and greater reducing sugar content under normal and stress conditions.ConclusionsPtrA/NINV is an important gene implicated in sucrose decomposition, and plays a positive role in abiotic stress tolerance by promoting osmotic adjustment, ROS detoxification and photosynthesis efficiency. Thus, PtrA/NINV has great potential to be used in transgenic breeding for improvement of stress tolerance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0761-0) contains supplementary material, which is available to authorized users.

Overexpression of an MYB-Related Gene FvMYB1 from Fraxinus velutina Increases Tolerance to Salt Stress in Transgenic Tobacco

MYB transcription factors (TFs) in plants play important roles in abiotic stress tolerance. Here, we report that an MYB-related TF gene, named FvMYB1, was isolated from the salt-tolerant tree species Fraxinus velutina Torr. The real-time PCR analysis showed that the FvMYB1 transcript increased remarkably in response to salt treatment. Subsequently, the FvMYB1 gene was transferred into the tobacco genome via the Agrobacterium-mediated approach. PCR and Southern blot verified that the FvMYB1 gene had been expressed in transgenic tobacco. The overexpressing transgenic seedlings displayed better salt tolerance in root length, shoot fresh weight, and shoot/root ratio compared to the wild type. Moreover, along with the superoxide dismutase and peroxidase activities and proline content that were significantly increased in the transgenic plants, the transcriptions of a series of stress-responsive genes were up-regulated under salt treatment. Further, an analysis of the upstream sequence of the FvMYB1 gene revealed that the promoter could enhance GUS gene expression in transgenic tobacco with NaCl treatment. These results indicate that FvMYB1 functions as a transcriptional activator that plays a regulatory role in salt stress tolerance of F. velutina.

Ectopic Expression of an Atypical Hydrophobic Group 5 LEA Protein from Wild Peanut, Arachis diogoi Confers Abiotic Stress Tolerance in Tobacco.

Late embryogenesis abundant (LEA) proteins are a group of hydrophilic proteins, which accumulate in plants under varied stress conditions like drought, salinity, extreme temperatures and oxidative stress suggesting their role in the protection of plants against these stresses. A transcript derived fragment (TDF) corresponding to LEA gene, which got differentially expressed in wild peanut, Arachis diogoi against the late leaf spot pathogen, Phaeoisariopsis personata was used in this study. We have cloned its full length cDNA by RACE-PCR, which was designated as AdLEA. AdLEA belongs to the atypical Group 5C of LEA protein family as confirmed by sequence analysis. Group 5C LEA protein subfamily contains Pfam LEA_2 domain and is highly hydrophobic. In native conditions, expression of AdLEA was upregulated considerably upon hormonal and abiotic stress treatments emphasizing its role in abiotic stress tolerance. Subcellular localization studies showed that AdLEA protein is distributed in both nucleus and cytosol. Ectopic expression of AdLEA in tobacco resulted in enhanced tolerance of plants to dehydration, salinity and oxidative stress with the transgenic plants showing higher chlorophyll content and reduced lipid peroxidation as compared to wild type plants. Overexpressed AdLEA tobacco plants maintained better photosynthetic efficiency under drought conditions as demonstrated by chlorophyll fluorescence measurements. These plants showed enhanced transcript accumulation of some stress-responsive genes. Our study also elucidates that ROS levels were significantly reduced in leaves and stomatal guard cells of transgenic plants upon stress treatments. These results suggest that AdLEA confers multiple stress tolerance to plants, which make it a potential gene for genetic modification in plants.

Characterization of nuclear cap binding complex protein genes (CBP20 and CBP80) from Brassica juncea

Nuclear cap binding complex proteins, CBP20 and CBP80, participate in mRNA transcript processing and also play an important role in abiotic stress tolerance. Brassica juncea is a major oilseed crop, and in this study, we reported the cloning and characterization of CBP20 and CBP80 genes from this species. A full-length BjCBP20 cDNA of 1075bp was cloned containing an open reading frame of 783bp encoding a polypeptide of 260 amino acids. Two genomic sequences of 1792bp and 1712bp were also cloned for BjCBP20, both of these having eight exons and seven introns. Likewise, 2538bp BjCBP80 sequence was cloned which encoded a protein sequence of 845 amino acids. Two genomic sequences of 5672bp and 5190bp consisting of eighteen exons and seventeen introns were cloned. Bioinformatics analysis of deduced proteins revealed the presence of the signature RRM domain in BjCBP20 and MIF4G domain in BjCBP80. Nuclear localization signal was present in BjCBP20. The phylogenetic analysis revealed less conservation in BjCBP80 than BjCBP20 when compared to proteins from other organisms. Expression analysis by qRT-PCR depicted steady levels of both the proteins in developmental stages. BjCBP80 showed highest expression in young leaves while lowest level of expression of BjCBP20 was seen in mature leaves. Under salt and osmotic stress, BjCBP80 level decreased initially and then regained back to normal levels. In osmotic stress, the BjCBP20 levels decreased while no significant change was observed under salt stress.

A consortium of rhizobacterial strains and biochemical growth elicitors improve cold and drought stress tolerance in rice (Oryza sativa L.).

In the present study, a consortium of two rhizobacteria Bacillus amyloliquefaciens Bk7 and Brevibacillus laterosporus B4, termed 'BB', biochemical elicitors salicylic acid and β-aminobutyric acid (SB) and their mixture (BBSB) were investigated for cold and drought stress tolerance in rice plants. After withholding water for 16days, rice plants treated with BBSB showed 100% survival, improved seedling height (35.4cm), shoot number (6.12), and showed minimum symptoms of chlorosis (19%), wilting (4%), necrosis (6%) and rolling of leaves. Similarly, BB inoculation enhanced plant growth and reduced overall symptoms in rice seedlings subjected to 0±5°C for 24h. Our results imply several mechanisms underlying BB- and BBSB-elicited stress tolerance. In contrast to the control, both treatments significantly decreased leaf monodehydroascorbate (MDA) content and electrolyte leakage, and increased leaf proline and cholorophyll content. Moreover, activities of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) increased 3.0- and 3.6-fold, respectively. Moreover, expression of OsMYB3R-2, OsDIL, OsDREB1A and OsCDPK13 genes was significantly up-regulated, suggesting that these genes play important roles in abiotic stress tolerance of rice. In addition, bacterial strains Bk7 and B4 were able to produce high amounts of IAA and siderophores, and colonise the plant roots, while only strain Bk7 exhibited the capability to form biofilms and solubilise inorganic phosphate. This study indicates that the BB and BBSB bio-formulations can be used to confer induced systematic tolerance and improve the health of rice plants subject to chilling and drought stress.

A bHLH gene from Tamarix hispida improves abiotic stress tolerance by enhancing osmotic potential and decreasing reactive oxygen species accumulation.

Basic helix-loop-helix (bHLH) leucine-zipper transcription factors play important roles in abiotic stress responses. However, their specific roles in abiotic stress tolerance are not fully known. Here, we functionally characterized a bHLH gene, ThbHLH1, from Tamarix hispida in abiotic stress tolerance. ThbHLH1 specifically binds to G-box motif with the sequence of 'CACGTG'. Transiently transfected T. hispida plantlets with transiently overexpressed ThbHLH1 and RNAi-silenced ThbHLH1 were generated for gain- and loss-of-function analysis. Transgenic Arabidopsis thaliana lines overexpressing ThbHLH1 were generated to confirm the gain- and loss-of-function analysis. Overexpression of ThbHLH1 significantly elevates glycine betaine and proline levels, increases Ca(2+) concentration and enhances peroxidase (POD) and superoxide dismutase (SOD) activities to decrease reactive oxygen species (ROS) accumulation. Additionally, ThbHLH1 regulates the expression of the genes including P5CS, BADH, CaM, POD and SOD, to activate the above physiological changes, and also induces the expression of stress tolerance-related genes LEAs and HSPs. These data suggest that ThbHLH1 induces the expression of stress tolerance-related genes to improve abiotic stress tolerance by increasing osmotic potential, improving ROS scavenging capability and enhancing second messenger in stress signaling cascades.

Role of polyamines in abiotic stress responses.

Abstract Many secondary metabolites in plants are involved in a range of plant physiological processes including abiotic stress tolerance. Major polyamine (PA) compounds including putrescine (Put), spermidine (Spd) and spermine (Spm) have structural, functional and regulatory activities that allow them to play a major role in abiotic stress tolerance. A thorough understanding of PA function in plant stress tolerance is important for improving plant stress responses, breeding, biomarker development and other purposes. In this review, I discuss the role of PA in several types of abiotic stress and the mechanisms associated with dynamic changes in PA content. Major methods to evaluate PA function are discussed including biosynthetic gene expression, exogenous application of PA, use of PA biosynthesis inhibitors, transgenic manipulation and development of gain or loss of function mutants.

Transcriptome-Based Analysis of Dof Family Transcription Factors and Their Responses to Abiotic Stress in Tea Plant (Camellia sinensis).

Tea plant (Camellia sinensis (L.) O. Kuntze) is affected by abiotic stress during its growth and development. DNA-binding with one finger (Dof) transcription factors (TFs) play important roles in abiotic stress tolerance of plants. In this study, a total of 29 putative Dof TFs were identified based on transcriptome of tea plant, and the conserved domains and common motifs of these CsDof TFs were predicted and analyzed. The 29 CsDof proteins were divided into 7 groups (A, B1, B2, C1, C2.1, C2.2, and D2), and the interaction networks of Dof proteins in C. sinensis were established according to the data in Arabidopsis. Gene expression was analyzed in “Yingshuang” and “Huangjinya” under four experimental stresses by qRT-PCR. CsDof genes were expressed differentially and related to different abiotic stress conditions. In total, our results might suggest that there is a potential relationship between CsDof factors and tea plant stress resistance.

Characterization and expression profile of CaNAC2 pepper gene.

The plant-specific NAC (NAM, ATAF, and CUC) transcription factors have diverse role in development and stress regulation. A new transcript encoding NAC protein, homologous to nam-like protein 4 from Petunia was identified from an ABA-regulated subtractive cDNA library of Capsicum annuum seedling. Here, this homolog (named CaNAC2) from C. annuum was characterized and investigated its role in abiotic stress tolerance. Our results indicated that a plant-specific and conserved NAC domain was located in the N-terminus domain of CaNAC2 which was predicted to encode a polypeptide of 410 amino acids. Phylogenetic analysis showed that CaNAC2 belonged to the NAC2 subgroup of the orthologous group 4d. The protein CaNAC2 was subcellularly localized in the nucleus and it had transcriptional activity in yeast cell. CaNAC2 was expressed mainly in seed and root. The transcription expression of CaNAC2 was strongly induced by cold, salt and ABA treatment and inhibited by osmotic stress and SA treatment. Silence of CaNAC2 in virus-induced gene silenced pepper seedlings resulted in the increased susceptibility to cold stress and delayed the salt-induced leaf chlorophyll degradation. These results indicated that this novel CaNAC2 gene might be involved in pepper response to abiotic stress tolerance.