Confers Drought Tolerance Research Articles

Function of Hevea brasiliensis NAC1 in dehydration-induced laticifer differentiation and latex biosynthesis.

HbNAC1 is a transcription factor in rubber plants whose expression is induced by dehydration, leading to latex biosynthesis. Laticifer is a special tissue in Hevea brasiliensis where natural rubber is biosynthesized and accumulated. In young stems of epicormic shoots, the differentiation of secondary laticifers can be induced by wounding, which can be prevented when the wounding site is wrapped. Using this system, differentially expressed genes were screened by suppression subtractive hybridization (SSH) and macroarray analyses. This led to the identification of several dehydration-related genes that could be involved in laticifer differentiation and/or latex biosynthesis, including a NAC transcription factor (termed as HbNAC1). Tissue sections confirmed that local tissue dehydration was a key signal for laticifer differentiation. HbNAC1 was localized at the nucleus and showed strong transcriptional activity in yeast, suggesting that HbNAC1 is a transcription factor. Furthermore, HbNAC1 was found to bind to the cis-element CACG in the promoter region of the gene encoding the small rubber particle protein (SRPP). Transgenic experiments also confirmed that HbNAC1 interacted with the SRPP promoter when co-expressed, and enhanced expression of the reporter gene β-glucuronidase occurred in planta. In addition, overexpression of HbNAC1 in tobacco plants conferred drought tolerance. Together, the data suggest that HbNAC1 might be involved in dehydration-induced laticifer differentiation and latex biosynthesis.

Improved drought tolerance by α-naphthaleneacetic acid-induced ROS accumulation in two soybean cultivars

Drought is a major abiotic factor limiting agricultural crop production. The objective of this study was to investigate whether α-naphthaleneacetic acid (NAA) confers drought tolerance to soybeans and if such tolerance is correlated with the early reactive oxygen species (ROS) accumulation in leaves. The plants of soybean (Glycine max [L.] Merr.) cv. Nannong 99-6 and cv. Kefeng 1 were foliar treated with 40 mg L−1 NAA at the beginning of bloom and then exposed to water stress for 10 d. We monitored changes in ROS levels, lipid peroxidation and antioxidant system as well as plant biomass during the drought treatment. The results showed that drought stress significantly depressed the growth and yield regardless of spraying NAA. However, drought-stressed plants treated with NAA showed much higher plant biomass and yield than those without NAA. The ROS levels increased in stressed Kefeng 1 but not in stressed Nannong 99-6 2–4 days after the treatment (DAT). During 6–10 DAT, stressed Kefeng 1 had greater increase in the levels of superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), γ-glutamylcysteine synthetase (γ-GCS), reduced ascorbate (AsA), and glutathione (GSH), smaller increase in ROS and malondialdehyde (MDA) as compared with stressed Nannong 99-6. Low ROS prevented ROS from directly reacting with membrane lipid during this stage and, consequently, reduced the cell damage. NAA application elevated ROS levels at 4 DAT, and then increased antioxidant capacity and blocked the increase in the MDA and ROS in stressed Nannong 99-6 and Kefeng 1. Overall, the results indicate that NAA application effectively alleviates the adverse effects of drought stress, which is partially attributable to increase in antioxidant ability and decrease in lipid peroxidation induced by the early ROS accumulation triggered by NAA.

Overexpression of an Arabidopsis cysteine-rich receptor-like protein kinase, CRK5, enhances abscisic acid sensitivity and confers drought tolerance.

Receptor-like kinases (RLKs) have been reported to regulate many developmental and defense process, but only a few members have been functionally characterized. In the present study, our observations suggest that one of the RLKs, a membrane-localized cysteine-rich receptor-like protein kinase, CRK5, is involved in abscisic acid (ABA) signaling in Arabidopsis thaliana Overexpression of CRK5 increases ABA sensitivity in ABA-induced early seedling growth arrest and promotion of stomatal closure and inhibition of stomatal opening. Interestingly, and importantly, overexpression of CRK5 enhances plant drought tolerance without affecting plant growth at the mature stages and plant productivity. Transgenic lines overexpressing a mutated form of CRK5, CRK5 (K372E) with the change of the 372nd conserved amino acid residue from lysine to glutamic acid in its kinase domain, result in wild-type ABA and drought responses, supporting the role of CRK5 in ABA signaling. The loss-of-function mutation of the CRK5 gene does not affect the ABA response, while overexpression of two homologs of CRK5, CRK4 and CRK19, confers ABA responses, suggesting that these CRK members function redundantly. We further showed that WRKY18, WRKY40 and WRKY60 transcription factors repress the expression of CRK5, and that CRK5 likely functions upstream of ABI2 in ABA signaling. These findings help in understanding the complex ABA signaling network.

Overexpression of sugarcane gene SoSnRK2.1 confers drought tolerance in transgenic tobacco.

Overexpression of SoSnRK2.1 improved drought tolerance and growth of tobacco plants. Sucrose non-fermenting1-related protein kinase 2 (SnRK2) is a key enzyme in regulating ABA signal transduction in plants, and it plays a significant role in response to multiple abiotic stresses. In this research, SoSnRK2.1 gene was cloned from sugarcane variety GT21 and characterized under various stresses. The cloned SoSnRK2.1 gene has a complete open reading frame of 1002bp, encoding a peptide of 333 amino acids. The amino acid sequence of SoSnRK2.1 has high homology with those of Zea mays and Oryza sativa, which belongs to SnRK2s families. The expression of SoSnRK2.1 under stresses of drought, PEG, and ABA indicated that this gene is involved in stress responses in sugarcane. To investigate the gene function, fusional SoSnRK2.1-GFP-pBI121 under control of CaMV 35S was transformed into tobacco plants. Growth and morphology of transgenic plants demonstrated that overexpression of SoSnRK2.1 enhanced drought tolerance in tobacco. Transgenic tobacco plants had lower levels of ion leakage (IL), and contents of maleic dialdehyde (MDA) and H2O2, with higher activities of three antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and chlorophyll and relative water content (RWC) than those in wide type (WT) tobacco. SoSnRK2.1 was stably transmitted to the next generation via sexual reproduction. Though the data presented here are from a heterologous system, it is highly likely that SoSnRK2.1 is involved in the abiotic stress response in sugarcane and may be playing an important role in regulation of its growth.

A SNARE-Like Superfamily Protein SbSLSP from the Halophyte Salicornia brachiata Confers Salt and Drought Tolerance by Maintaining Membrane Stability, K(+)/Na(+) Ratio, and Antioxidant Machinery.

About 1000 salt-responsive ESTs were identified from an extreme halophyte Salicornia brachiata. Among these, a novel salt-inducible gene SbSLSP (Salicornia brachiata SNARE-like superfamily protein), showed up-regulation upon salinity and dehydration stress. The presence of cis-regulatory motifs related to abiotic stress in the putative promoter region supports our finding that SbSLSP gene is inducible by abiotic stress. The SbSLSP protein showed a high sequence identity to hypothetical/uncharacterized proteins from Beta vulgaris, Spinacia oleracea, Eucalyptus grandis, and Prunus persica and with SNARE-like superfamily proteins from Zostera marina and Arabidopsis thaliana. Bioinformatics analysis predicted a clathrin adaptor complex small-chain domain and N-myristoylation site in the SbSLSP protein. Subcellular localization studies indicated that the SbSLSP protein is mainly localized in the plasma membrane. Using transgenic tobacco lines, we establish that overexpression of SbSLSP resulted in elevated tolerance to salt and drought stress. The improved tolerance was confirmed by alterations in a range of physiological parameters, including high germination and survival rate, higher leaf chlorophyll contents, and reduced accumulation of Na+ ion and reactive oxygen species (ROS). Furthermore, overexpressing lines also showed lower water loss, higher cell membrane stability, and increased accumulation of proline and ROS-scavenging enzymes. Overexpression of SbSLSP also enhanced the transcript levels of ROS-scavenging and signaling enzyme genes. This study is the first investigation of the function of the SbSLSP gene as a novel determinant of salinity/drought tolerance. The results suggest that SbSLSP could be a potential candidate to increase salinity and drought tolerance in crop plants for sustainable agriculture in semi-arid saline soil.

OsMSR15 encoding a rice C2H2-type zinc finger protein confers enhanced drought tolerance in transgenic Arabidopsis

Zinc nger proteins (ZFPs) play important roles in plant responses to biotic and abiotic stresses. Through microarray analysis, an Oryza sativa L. multi-stress-responsive gene, OsMSR15, was identied and subsequently cloned from rice Pei’ai 64S (Oryza sativa L.). Expression of OsMSR15 was strongly up-regulated by cold, drought and heat stresses in different tissues at different developmental stages of rice. OsMSR15 contains two C2H2-type zinc nger motifs, a nuclear localization signal (B box), a Leu-rich domain (L-box) and a conserved EAR-motif close to its C-terminus. The OsMSR15-GFP fusion protein was localized to the nucleus. Yeast-one hybrid assay showed that OsMSR15 possesses transcriptional activation ability. Expression of OsMSR15 in Arabidopsis conferred drought tolerance, and transgenic plants showed hypersensitivity to exogenous ABA during the seed germination and post-germination stages. Transgenic plants also showed higher levels of free proline, less electrolyte leakage and increased expressions of a number of stress-responsive genes, including LEA3, RD29A, DREB1A and P5CS1 under drought stress. The obtained results indicate that OsMSR15 is an important regulator involved in plant response to drought stress.

English

Drought is one of the most important stress factors which adversely affect plants’ growth and productivity. Global climate change may make this situation more serious in the years ahead. Considering the long time span required for the generation of drought resistant genotypes in Rubber (Hevea brasiliensis) through conventional breeding, molecular interventions to engineer plants to have either drought responsive genes or genes expected to alter osmotic regulation would be very attractive. The glyoxalase pathway involving glyoxalase I and glyoxalase II enzymes is required for glutathione-based detoxification of methylglyoxal. In this study the effects of various abiotic stresses on the up-regulation of methylglyoxal levels and glyoxalase I activities in Hevea brasiliensis seedlings were investigated. Most of the stresses caused significant increase in methylglyoxal level and glyoxalase I activity, among which drought caused the highest induction of glx I followed by salinity, 2, 4-D, ABA, methylglyoxal, white light and CdCl2. The stress-induced increases in methylglyoxal and glyoxalase I activity found in the present study suggest an important role of glyoxalase I in conferring drought tolerance. The up-regulation of glyoxalase I under drought stress indicates its future utility in developing tolerance to drought stress in Hevea brasiliensis. In the present study, a partial cDNA sequence coding for glyoxalase I was amplified by PCR using specific primers. The 440 bp cDNA amplicon obtained was sequenced and subjected to online BLAST analysis. The sequence of Hevea brasiliensis glyoxalase I (GenBank Acc. No: GU598520) had six open reading frames. The ORF finder revealed the longest ORF of 336 bp. Glyoxalase I from Ricinus communis had the highest nucleotide sequence homology (90%) compared to the amplified gene. BLASTP analysis also showed high homology between the deduced protein sequence of the amplified gene and glyoxalases from other species. Our results suggest that the multi-stress inducibility of glyoxalase I in the present study may be due to the fact that it might protect the plants against MG that is formed under various stresses including drought and confers tolerance by increasing the GSH-based detoxification system and decreasing lipid peroxidation Key words: Glyoxalase I, Hevea brasiliensis, Methylglyoxal, drought tolerance, abiotic stress.

Ectopic expression of a tobacco vacuolar invertase inhibitor in guard cells confers drought tolerance in Arabidopsis

There are several hypotheses that explain stomatal behavior. These include the concept of osmoregulation mediated by potassium and its counterions malate and chlorine and the more recent starch–sugar hypothesis. We have previously reported that the activity of the sucrose cleavage enzyme, vacuolar invertase (VIN), is significantly higher in guard cells than in other leaf epidermal cells and its activity is correlated with stomatal aperture. Here, we examined whether VIN indeed controls stomatal movement under normal and drought conditions by transforming Arabidopsis with a tobacco vacuolar invertase inhibitor homolog (Nt-inhh) under the control of an abscisic acid-sensitive and guard cell-specific promoter (AtRab18). The data obtained showed that guard cells of transgenic Arabidopsis plants had lower VIN activity, stomatal aperture and conductance than that of wild-type plants. Moreover, the transgenic plants also displayed higher drought tolerance than wild-type plants. The data indicate that VIN is a promising target for manipulating stomatal function to increase drought tolerance.

Expression of Arabidopsis Bax Inhibitor-1 in transgenic sugarcane confers drought tolerance.

SummaryThe sustainability of global crop production is critically dependent on improving tolerance of crop plants to various types of environmental stress. Thus, identification of genes that confer stress tolerance in crops has become a top priority especially in view of expected changes in global climatic patterns. Drought stress is one of the abiotic stresses that can result in dramatic loss of crop productivity. In this work, we show that transgenic expression of a highly conserved cell death suppressor, Bax Inhibitor‐1 from Arabidopsis thaliana (AtBI‐1), can confer increased tolerance of sugarcane plants to long‐term (>20 days) water stress conditions. This robust trait is correlated with an increased tolerance of the transgenic sugarcane plants, especially in the roots, to induction of endoplasmic reticulum (ER) stress by the protein glycosylation inhibitor tunicamycin. Our findings suggest that suppression of ER stress in C4 grasses, which include important crops such as sorghum and maize, can be an effective means of conferring improved tolerance to long‐term water deficit. This result could potentially lead to improved resilience and yield of major crops in the world.

Heterologous Expression of AtWRKY57 Confers Drought Tolerance in Oryza sativa

Drought stress is a severe environmental factor that greatly restricts plant distribution and crop production. Recently, we have found that overexpressing AtWRKY57 enhanced drought tolerance in Arabidopsis thaliana. In this study, we further reported that the Arabidopsis WRKY57 transcription factor was able to confer drought tolerance to transgenic rice (Oryza sativa) plants. The enhanced drought tolerance of transgenic rice was resulted from the lower water loss rates, cell death, malondialdehyde contents and relative electrolyte leakage while a higher proline content and reactive oxygen species-scavenging enzyme activities was observed during stress conditions. Moreover, further investigation revealed that the expression levels of several stress-responsive genes were up-regulated in drought-tolerant transgenic rice plants, compared with those in wild-type plants. In addition to the drought tolerance, the AtWRKY57 over-expressing plants also had enhanced salt and PEG stress tolerances. Taken together, our study indicates that over-expressing AtWRKY57 in rice improved not only drought tolerance but also salt and PEG tolerance, demonstrating its potential role in crop improvement.

Characterization of the Promoter of the Homeobox Gene CaHB12 in Coffea arabica

Abiotic stresses, especially drought, are major bottlenecks for crop production. The CaHB12 gene codes for a transcription factor belonging to the HD-Zip family, and this gene was found to be induced by drought conditions in Coffea arabica. The overexpression of CaHB12 confers drought tolerance to transgenic Arabidopsis thaliana plants. In this study, the promoter of CaHB12 was isolated and characterized. Two different promoter sequences were identified in C. arabica, a tetraploid species. Cloning and sequencing of the HB12 promoter regions of the ancestral species C. canephora and C. eugenioides suggest that the C. arabica sequences originated from the diploid parental ancestors. In silico promoter analysis showed typical cis-elements for responses to drought, salinity and abscisic acid in both sequences identified in the C. arabica genome. The expression activity of two fragments from each promoter, referred to as pCc_CaHB12–979, pCc_CaHB12–356, pCe_CaHB12–749 and pCe_CaHB12–356, were investigated using uidA as the reporter gene in transgenic A. thaliana plants. In plants bearing the pCc_CaHB12–979::GUS construct, GUS activity was observed in leaves during drought stress and in roots after treatment with polyethylene glycol or mannitol. The pCc_CaHB12 (356 bp) promoter fragment showed activity after treatment with ABA. Real-time qPCR analysis of the uidA gene was used to quantify expression of the promoter fragments. Interestingly, the two pCe_CaHB12 promoter fragments showed no activity under the experimental conditions tested. These results suggest that the CaHB12 gene is stress-inducible and regulated by the pCc_CaHB12 promoter, a sequence putatively inherited from the drought-tolerant coffee species C. canephora.

Identification and Validation of Selected Universal Stress Protein Domain Containing Drought-Responsive Genes in Pigeonpea (Cajanus cajan L.).

Pigeonpea is a resilient crop, which is relatively more drought tolerant than many other legume crops. To understand the molecular mechanisms of this unique feature of pigeonpea, 51 genes were selected using the Hidden Markov Models (HMM) those codes for proteins having close similarity to universal stress protein domain. Validation of these genes was conducted on three pigeonpea genotypes (ICPL 151, ICPL 8755, and ICPL 227) having different levels of drought tolerance. Gene expression analysis using qRT-PCR revealed 6, 8, and 18 genes to be ≥2-fold differentially expressed in ICPL 151, ICPL 8755, and ICPL 227, respectively. A total of 10 differentially expressed genes showed ≥2-fold up-regulation in the more drought tolerant genotype, which encoded four different classes of proteins. These include plant U-box protein (four genes), universal stress protein A-like protein (four genes), cation/H(+) antiporter protein (one gene) and an uncharacterized protein (one gene). Genes C.cajan_29830 and C.cajan_33874 belonging to uspA, were found significantly expressed in all the three genotypes with ≥2-fold expression variations. Expression profiling of these two genes on the four other legume crops revealed their specific role in pigeonpea. Therefore, these genes seem to be promising candidates for conferring drought tolerance specifically to pigeonpea.

Genetic Variability and AMMI Bi-Plot Analysis in Bread Wheat Based on Multi-location Trials Conducted under Drought Conditions across Agro-climatic Zones of India

Wheat grown globally under different agro-ecological conditions and drought conditions has emerged as a priority research area for developing genotypes in the near future. In this research, 36 genotypes, including checks (HW 2004, HD 2888, PBW 175 and NI 5439) were tested at 12 locations covering four mega wheat growing zones of India, followed by augmented design under drought conditions, during the crop season 2012/13. The main objective of this research was: to estimate variability parameters and correlation; determining the closeness of experimental sites; and identification of site specific adapted wheat genotypes. Our research findings revealed higher broad-sense heritability for plant height (89-98%) and thousand grain weight (80-93%) in all four zones of India. Herein positive and significant phenotypic correlation was found between thousand grain weight and grain yield; while days to heading, days to maturity and plant height were negatively correlated with grain yield under peninsular zone comparable to other zones. Based upon mean yield across locations, the genotypes MACS 6348 (25 q/ha); HD 3043 and AKAW 4635 (24 q/ha each) were found better than others. AMMI analysis revealed that locations; Kota, Sagar, Indore and Niphad were very close to each other and five genotypes were found to be stable in these locations. The locations; Ranchi, Delhi, Gurdaspur and Pune had also been very close to each other and we have identified seven stable genotypes for these locations. Our findings would be very spectacular for wheat breeders conducting multi-location trials. Herein; the promising genotypes identified for different locations could serve as donors to develop the multi-parent advanced generation integrated cross populations to stack genes/alleles conferring drought tolerance.

Comparative miRNAome Analysis Revealed Numerous Conserved and Novel Drought Responsive miRNAs in Cotton (<i>Gossypium spp.</i>)

Negative regulations of gene expression by endogenous, non-coding miRNAs have been shown to play important role in abiotic stress responses in plants. However, limited knowledge is available on water stress responsive miRNAs in cotton. In this study, differentially expressed drought responsive miRNAs and their targets were identified under natural field conditions through high-throughput small RNA sequencing by comparing leaf samples of drought tolerant Gossypium hirsutum cv. KC3 and drought susceptible G. barbadense cv. Suvin. Totally four small RNA libraries were constructed and sequenced by employing ion proton TM technology. Altogether, there were 39 407 089 reads with a mean read length of 22 nt. In KC3, there were 5 138 unique miRNA reads that were differentially expressed with at least two folds under water stressed conditions. In contrast, Suvin have shown 8 469 unique miRNA reads that were differentially expressed with minimum of two folds under water stressed conditions. Comparison of miRNAs expressed under water stressed conditions between KC3 and Suvin, have resulted 7 494 miRNA reads and interestingly majority of them were down regulated with at least two folds. Besides identifying large numbers of novel miRNAs, several abiotic stress responsive conserved miRNAs were also noticed. Of particular interest were miR750, miR2, miR14, miR276, miR279, miR-bantam and miR5176 that were highly down regulated in KC3 under water stress conditions. Strikingly, miR2 and miR-bantam were previously shown to target pre-apoptotic genes in biological systems. Further, the identified miRNAs were also targeting different classes of dehydrogenases, protein kinases and transcription factors. Our results revealed for the first time that there were large numbers of water stress related miRNAs that might be sequentially and/or complexly involved in gene regulation that confers drought tolerance in cotton under field conditions and they have enormous potential in elucidating the molecular mechanism of miRNA based gene regulation and more importantly in genetic improvement of drought tolerance in cotton. Further, this is the first report on experimentally identifying miRNAs in G. barbadense .

Identification of microsatellite markers linked to drought tolerance in rice (Oryza sativa L.) through bulked line analysis

Identification of donor parents and markers for traits conferring drought tolerance eventually hastens the breeding for drought tolerance in rice. The extent of variation for water stress indicators, physio-morphological and plant production traits were assessed by evaluating 36 rice genotypes under water stress condition. Significant variation was observed for these traits and thirteen drought tolerant and susceptible genotypes were selected and grouped as tolerant and susceptible bulks based on physio-morphological and biochemical characterization. Genomic DNA was isolated from these rice accessions and pooled, respectively into drought tolerant and susceptible bulks. Bulked line analysis was carried to identify microsatellite markers linked to drought tolerance in rice. Out of 200 SSR primers screened RM 1092; RM 129 and RM157B were polymorphic between the bulks and also co-segregated among the individual genotypes constituting the respective bulks. The genomic regions flanked by these markers have been identified to be associated with various drought tolerance traits in rice and can be useful for marker assisted selection for drought resistance improvement in rice. The genotypes identified as drought tolerant can be used us donars in drought improvement breeding programmes. Key words Rice, drought resistance, microsatellite markers, bulk line analysis

The alterations of endogenous polyamines and phytohormones induced by exogenous application of spermidine regulate antioxidant metabolism, metallothionein and relevant genes conferring drought tolerance in white clover

Cross-talk between polyamines (PAs) and phytohormones may be involved in the regulation of drought tolerance in plants. The objective of this study was to determine the effects of exogenous spermidine (Spd) and a Spd inhibitor, dimethylthiourea (DCHA), on drought responses of white clover (Trifolium repens). Metabolic, protein, and gene transcript levels were evaluated at leaf relative water content levels of 87% for non-stressed plants and 50% for drought-stressed plants. The exogenous application of Spd (0.05mM) significantly increased endogenous PAs content whereas DCHA generally reduced PAs content. Phytohormone responses to Spd application included an elevated gibberellic acid (GA) and indole-3-acetic acid (IAA) content under non-stressed condition, and an increased GA and cytokinin (CTK) content as well as decreased IAA content under water deficit condition. The increase in endogenous PAs had no significant effect on abscisic acid (ABA) accumulation under either water treatment. Spd treatment resulted in enhanced antioxidant defense via maintenance of greater antioxidant enzyme activities and transcript levels, especially ascorbic acid (AsA). Other metabolites such as total phenols, flavonoids, proline, metallothionein (MT), and cysteine (Cyt) were also elevated with Spd treatment. On the contrary, inhibition of Spd biosynthesis weakened antioxidant defense, decreased proline metabolism, and inhibited MT genes expression leading to aggravation of drought-induced stress damages. These results suggest that changes of PAs and phytohormones play critical roles in the improvement of drought tolerance in white clover, which are attributed to the alleviation of oxidative stress, inhibition of leaf senescence, and maintenance of growth under drought stress.

Drought tolerance and proteomics studies of transgenic wheat containing the maize C4 phosphoenolpyruvate carboxylase (PEPC) gene.

Enhancing drought tolerance of crops has been a great challenge in crop improvement. Here, we report the maize phosphoenolpyruvate carboxylase (PEPC) gene was able to confer drought tolerance and increase grain yield in transgenic wheat (Triticum aestivum L.) plants. The improved of drought tolerance was associated with higher levels of proline, soluble sugar, soluble protein, and higher water use efficiency. The transgenic wheat plants had also a more extensive root system as well as increased photosynthetic capacity during stress treatments. The increased grain yield of the transgenic wheat was contributed by improved biomass, larger spike and grain numbers, and heavier 1000-grain weight under drought-stress conditions. Under non-stressed conditions, there were no significant increases in these of the measured traits except for photosynthetic rate when compared with parental wheat. Proteomic research showed that the expression levels of some proteins, including chlorophyll A-B binding protein and pyruvate, phosphate dikinase, which are related to photosynthesis, PAP fibrillin, which is involved in cytoskeleton synthesis, S-adenosylmethionine synthetase, which catalyzes methionine synthesis, were induced in the transgenic wheat under drought stress. Additionally, the expression of glutamine synthetase, which is involved in ammonia assimilation, was induced by drought stress in the wheat. Our study shows that PEPC can improve both stress tolerance and grain yield in wheat, demonstrating the efficacy of PEPC in crop improvement.

Pseudomonas putida attunes morphophysiological, biochemical and molecular responses in Cicer arietinum L. during drought stress and recovery

Drought is one of the most important abiotic stresses that adversely affect plant growth and yield potential. However, some drought resistant rhizosphere competent bacteria are known to improve plant health and promote growth during abiotic stresses. Present study showed the role of Pseudomonas putida MTCC5279 (RA) in ameliorating drought stress on cv. BG-362 (desi) and cv. BG-1003 (kabuli) chickpea cultivars under in vitro and green house conditions. Polyethylene glycol-induced drought stress severely affected seed germination in both cultivars which was considerably improved on RA-inoculation. Drought stress significantly affected various growth parameters, water status, membrane integrity, osmolyte accumulation, ROS scavenging ability and stress-responsive gene expressions, which were positively modulated upon application of RA in both chickpea cultivars. Quantitative real-time (qRT)-PCR analysis showed differential expression of genes involved in transcription activation (DREB1A and NAC1), stress response (LEA and DHN), ROS scavenging (CAT, APX, GST), ethylene biosynthesis (ACO and ACS), salicylic acid (PR1) and jasmonate (MYC2) signalling in both chickpea cultivars exposed to drought stress and recovery in the presence or absence of RA. The observations imply that RA confers drought tolerance in chickpea by altering various physical, physiological and biochemical parameters, as well as by modulating differential expression of at least 11 stress-responsive genes. To the best of our knowledge, this is the first report on detailed analysis of plant growth promotion and stress alleviation in one month old desi and kabuli chickpea subjected to drought stress for 0, 1, 3 and 7 days and recovery in the presence of a PGPR.

Major latex protein-like protein 43 (MLP43) functions as a positive regulator during abscisic acid responses and confers drought tolerance in Arabidopsis thaliana.

Drought stress is one of the disadvantageous environmental conditions for plant growth and reproduction. Given the importance of abscisic acid (ABA) to plant growth and abiotic stress responses, identification of novel components involved in ABA signalling transduction is critical. In this study, we screened numerous Arabidopsis thaliana mutants by seed germination assay and identified a mutant mlp43 (major latex protein-like 43) with decreased ABA sensitivity in seed germination. The mlp43 mutant was sensitive to drought stress while the MLP43-overexpressed transgenic plants were drought tolerant. The tissue-specific expression pattern analysis showed that MLP43 was predominantly expressed in cotyledons, primary roots and apical meristems, and a subcellular localization study indicated that MLP43 was localized in the nucleus and cytoplasm. Physiological and biochemical analyses indicated that MLP43 functioned as a positive regulator in ABA- and drought-stress responses in Arabidopsis through regulating water loss efficiency, electrolyte leakage, ROS levels, and as well as ABA-responsive gene expression. Moreover, metabolite profiling analysis indicated that MLP43 could modulate the production of primary metabolites under drought stress conditions. Reconstitution of ABA signalling components in Arabidopsis protoplasts indicated that MLP43 was involved in ABA signalling transduction and acted upstream of SnRK2s by directly interacting with SnRK2.6 and ABF1 in a yeast two-hybrid assay. Moreover, ABA and drought stress down-regulated MLP43 expression as a negative feedback loop regulation to the performance of MLP43 in ABA and drought stress responses. Therefore, this study provided new insights for interpretation of physiological and molecular mechanisms of Arabidopsis MLP43 mediating ABA signalling transduction and drought stress responses.

SpBADH of the halophyte Sesuvium portulacastrum strongly confers drought tolerance through ROS scavenging in transgenic Arabidopsis

Glycine betaine (GB) accumulation is involved in abiotic stress. However, it is not known whether BADH, the key enzyme of GB synthesis, utilizes the antioxidant system to confer drought stress tolerance. In this study, a novel member of the ALDH10 gene family, SpBADH, was isolated from Sesuvium portulacastrum. The expression of this gene was up-regulated by NaCl, PEG6000, H2O2, ABA and high temperature in S. portulacastrum. SpBADH overexpression in Arabidopsis resulted in higher BADH activity and GB content and might increase tolerance to drought/osmotic stresses, specifically strong tolerance to drought stress. Transgenic lines exhibited lower MDA and H2O2 contents but higher proline, POD, SOD and CAT contents than the wild type under drought and osmotic stresses. SpBADH overexpression in Arabidopsis also enhanced the expression of ROS-related genes including AtSOD, AtPOD, AtCAT, AtAPX and Atpsb under drought and osmotic stresses. Thus, SpBADH increases plant tolerance to drought or osmotic stresses by reducing H2O2, increasing proline, and activating antioxidative enzymes to improve ROS scavenging.