Dehydration responsive element binding (DREB) factors or CRT element binding factors (CBFs) are members of the AP2/ERF family, which comprises a large number of stress-responsive regulatory genes. ...This review traverses almost two decades of research, from the discovery of DREB/CBF factors to their optimization for application in plant biotechnology. In this review, we describe (i) the discovery, classification, structure, and evolution of DREB genes and proteins; (ii) induction of DREB genes by abiotic stresses and involvement of their products in stress responses; (iii) protein structure and DNA binding selectivity of different groups of DREB proteins; (iv) post-transcriptional and post-translational mechanisms of DREB transcription factor (TF) regulation; and (v) physical and/or functional interaction of DREB TFs with other proteins during plant stress responses. We also discuss existing issues in applications of DREB TFs for engineering of enhanced stress tolerance and improved performance under stress of transgenic crop plants.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Halophytes are plants which naturally survive in saline environment. They account for ∼1% of the total flora of the world. They include both dicots and monocots and are distributed mainly in arid, ...semi-arid inlands and saline wet lands along the tropical and sub-tropical coasts. Salinity tolerance in halophytes depends on a set of ecological and physiological characteristics that allow them to grow and flourish in high saline conditions. The ability of halophytes to tolerate high salt is determined by the effective coordination between various physiological processes, metabolic pathways and protein or gene networks responsible for delivering salinity tolerance. The salinity responsive proteins belong to diverse functional classes such as photosynthesis, redox homeostasis; stress/defense, carbohydrate and energy metabolism, protein metabolism, signal transduction and membrane transport. The important metabolites which are involved in salt tolerance of halophytes are proline and proline analog (4-hydroxy-N-methyl proline), glycine betaine, pinitol, myo-inositol, mannitol, sorbitol, O-methylmucoinositol, and polyamines. In halophytes, the synthesis of specific proteins and osmotically active metabolites control ion and water flux and support scavenging of oxygen radicals under salt stress condition. The present review summarizes the salt tolerance mechanisms of halophytes by elucidating the recent studies that have focused on proteomic, metabolomic, and ionomic aspects of various halophytes in response to salinity. By integrating the information from halophytes and its comparison with glycophytes could give an overview of salt tolerance mechanisms in halophytes, thus laying down the pavement for development of salt tolerant crop plants through genetic modification and effective breeding strategies.
Kappaphycus alvarezii
sap (K-sap) facilitates plant growth in stressful environments by regulating the stress signalling components of the plant system. In the present study, the effect of K-sap on ...three durum wheat varieties, commercially important for pasta and semolina is studied in response to salt and drought stress during both vegetative and reproductive growth phases. The application of K-sap contributed to the improvement of the morphological, physio-biochemical parameters and gene expression facilitating improved growth and yield. Under salt stress, K-sap-treated plants maintained lower Na
+
/K
+
ratio and higher Ca
2+
content. During stress, K-sap reduced cell membrane damage by maintaining higher tissue water content, reduced electrolyte leakage and reduced malondialdehyde contents. Reactive oxygen species, superoxide and peroxide contents were also significantly reduced on K-sap treatment. Osmoprotectants such as total proteins, proline, amino acids and soluble sugars increased with K-sap application both with and without stress. The phytohormones abscisic acid, cytokinin and auxin were significantly regulated by K-sap application. qPCR analysis showed enhanced expression of stress-responsive wheat MAP kinase, WRKY transcription factor and antioxidative genes with K-sap treatment during stress. The application of K-sap significantly improved yield by increasing number of spikes and grains. Here, we report for the first time the integrative study of metabolic components coordinated by genes and hormones to reveal the mechanism of K-sap in durum wheat for improving yield and stress tolerance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Soil salinity adversely affects plant growth and development and disturbs intracellular ion homeostasis resulting cellular toxicity. The Salt Overly Sensitive 1 (SOS1) gene encodes a plasma membrane ...Na(+)/H(+) antiporter that plays an important role in imparting salt stress tolerance to plants. Here, we report the cloning and characterisation of the SbSOS1 gene from Salicornia brachiata, an extreme halophyte.
The SbSOS1 gene is 3774 bp long and encodes a protein of 1159 amino acids. SbSOS1 exhibited a greater level of constitutive expression in roots than in shoots and was further increased by salt stress. Overexpressing the S. brachiata SbSOS1 gene in tobacco conferred high salt tolerance, promoted seed germination and increased root length, shoot length, leaf area, fresh weight, dry weight, relative water content (RWC), chlorophyll, K(+)/Na(+) ratio, membrane stability index, soluble sugar, proline and amino acid content relative to wild type (WT) plants. Transgenic plants exhibited reductions in electrolyte leakage, reactive oxygen species (ROS) and MDA content in response to salt stress, which probably occurred because of reduced cytosolic Na(+) content and oxidative damage. At higher salt stress, transgenic tobacco plants exhibited reduced Na(+) content in root and leaf and higher concentrations in stem and xylem sap relative to WT, which suggests a role of SbSOS1 in Na(+) loading to xylem from root and leaf tissues. Transgenic lines also showed increased K(+) and Ca(2+) content in root tissue compared to WT, which reflect that SbSOS1 indirectly affects the other transporters activity.
Overexpression of SbSOS1 in tobacco conferred a high degree of salt tolerance, enhanced plant growth and altered physiological and biochemical parameters in response to salt stress. In addition to Na(+) efflux outside the plasma membrane, SbSOS1 also helps to maintain variable Na(+) content in different organs and also affect the other transporters activity indirectly. These results broaden the role of SbSOS1 in planta and suggest that this gene could be used to develop salt-tolerant transgenic crops.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abiotic and biotic stresses negatively influence survival, biomass production and crop yield. Being multigenic as well as a quantitative trait, it is a challenge to understand the molecular basis of ...abiotic stress tolerance and to manipulate it as compared to biotic stresses. Lately, some transcription factor(s) that regulate the expression of several genes related to stress have been discovered. One such class of the transcription factors is DREB/CBF that binds to drought responsive cis-acting elements. DREBs belong to ERF family of transcription factors consisting of two subclasses, i.e. DREB1/CBF and DREB2 that are induced by cold and dehydration, respectively. The DREBs are apparently involved in biotic stress signaling pathway. It has been possible to engineer stress tolerance in transgenic plants by manipulating the expression of DREBs. This opens an excellent opportunity to develop stress tolerant crops in future. This review intends to focus on the structure, role of DREBs in plant stress signaling and the present status of their deployment in developing stress tolerant transgenic plants.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Sesame (
Sesamum indicum
L.) is the oldest important edible oilseed crop found throughout many tropical and subtropical regions of the world. India ranks second in its domestication with a total ...production of 0.67 million tons. The growth index of sesame in Asia, Africa, and South and Central America is 54.9%, 40.8%, and 4.3%, respectively. The crop has high economic potential but stress factors like temperature sensitivity, early senescence, pest attack, water logging, and disease infestations limit its productivity worldwide. Its recalcitrant nature, sexual incompatibility, and post fertilization barriers greatly restrict the generation of new varieties,
via
tissue culture and traditional breeding strategies. Thus, genetic engineering appears to be the best alternative to improve its yield by developing stress-tolerant plants. The callus induction and regeneration frequency in sesame is highly genotype dependent. Regeneration is observed in different cultivars
via
callus phase or directly from different explants mainly on Murashige and Skoog basal medium (MS) with high cytokinin and low auxin concentrations. The attempts towards developing genetic transformation protocols has resulted in very limited success. The present review highlights the history and discusses the detailed progress of sesame tissue culture and genetic transformation research with respect to genotype dependency, different medium compositions, plant hormones, and explant age.
Genetic engineering of plants for abiotic stress tolerance is a challenging task because of its multifarious nature. Comprehensive studies for developing abiotic stress tolerance are in progress, ...involving genes from different pathways including osmolyte synthesis, ion homeostasis, antioxidative pathways, and regulatory genes. In the last decade, several attempts have been made to substantiate the role of “single-function” gene(s) as well as transcription factor(s) for abiotic stress tolerance. Since, the abiotic stress tolerance is multigenic in nature, therefore, the recent trend is shifting towards genetic transformation of multiple genes or transcription factors. A large number of crop plants are being engineered by abiotic stress tolerant genes and have shown the stress tolerance mostly at laboratory level. This review presents a mechanistic view of different pathways and emphasizes the function of different genes in conferring salt tolerance by genetic engineering approach. It also highlights the details of successes achieved in developing salt tolerance in plants thus far.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Heterologous expression of fruit specific E8 promoter was observed in cucumber fruit.•The BsPhy is able to increase nutrients by phytate hydrolysis in transgenic cucumbers.•The fruit ...specific phytase expression was potentially higher in cucumber fruits.
The fruit nutrigenomics is an interesting and important research area towards nutrition enhancement. The phytic acid is one of the major antinutrient compound, present in seeded fruits and crops. It hinders the absorption of iron (Fe), zinc (Zn), magnesium (Mg), potassium (K) and calcium (Ca), causing mineral deficiencies. In the present study, the BsPhy gene was overexpressed in the cucumber fruits using the tomato fruit specific E8 and constitutive CaMV 35S promoter. The E8 promoter imparted heterologous expression of GUS gene in cucumber fruits, furthermore, the fruit specific expression of E8 promoter with BsPhy gene was confirmed in transgenics (E8::BsPhy) using anti rabbit-phytase antibody. The physio-biochemical analysis of transgenics revealed, maximum phytase activity in E8::BsPhy cucumber fruits at 10 days after anthesis (DAA) compared to 35S::BsPhy and wild-type (WT) fruits. Consequently, E8::BsPhy fruits also showed increased amount of inorganic phosphorus (Pi), total phosphorus (P), minerals (Zn, Fe, Mg, K, Ca), total carotenoid and other macronutrients at 10 DAA compared to 35S::BsPhy fruits. The metabolite profiling of fruits (10 DAA) showed increased sugars, amino acids, sugar acids and polyols, in both E8::BsPhy and 35S::BsPhy transgenics suggesting higher phytate metabolism, compared to WT fruits. Interestingly, both the transgenic fruits showed higher fruit biomass and yield along with improved nutritional quality, which can be attributed to increased P and Zn contents in transgenic fruits, compared to WT fruits. Our findings reveal that the BsPhy gene enhances minerals and macronutrients in transgenic cucumber fruits making it nutritious and healthy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Salinity adversely affects plant growth and development. Halotolerant plant-growth-promoting rhizobacteria (PGPR) alleviate salt stress and help plants to maintain better growth. In the present ...study, six PGPR strains were analyzed for their involvement in salt-stress tolerance in Arachis hypogaea. Different growth parameters, electrolyte leakage, water content, biochemical properties, and ion content were analyzed in the PGPR-inoculated plants under 100 mM NaCl. Three bacterial strains, namely, Brachybacterium saurashtrense (JG-06), Brevibacterium casei (JG-08), and Haererohalobacter (JG-11), showed the best growth of A. hypogaea seedlings under salt stress. Plant length, shoot length, root length, shoot dry weight, root dry weight, and total biomass were significantly higher in inoculated plants compared to uninoculated plants. The PGPR-inoculated plants were quite healthy and hydrated, whereas the uninoculated plant leaves were desiccated in the presence of 100 mM NaCl. The percentage water content (PWC) in the shoots and roots was also significantly higher in inoculated plants compared to uninoculated plants. Proline content and soluble sugars were significantly low, whereas amino acids were higher than in uninoculated plants. The MDA content was higher in uninoculated plants than in inoculated plants at 100 mM NaCl. The inoculated plants also had a higher K^sup +^/Na^sup +^ ratio and higher Ca^sup 2+^, phosphorus, and nitrogen content. The auxin concentration was higher in both shoot and root explants in the inoculated plants. Therefore, it could be predicted that all these parameters cumulatively improve plant growth under saline conditions in the presence of PGPR. This study shows that PGPR play an important role in inducing salinity tolerance in plants and can be used to grow salt-sensitive crops in saline areas.PUBLICATION ABSTRACT
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Salinity is one of the major factors negatively affecting crop productivity. WRKY transcription factors (TFs) are involved in salicylic acid (SA) mediated cellular reactive oxygen species homeostasis ...in response to different stresses, including salinity. Therefore, the effect of NaCl, NaCl + SA and SA treatments on different photosynthesis-related parameters and wax metabolites were studied in the Jatropha curcas WRKY (JcWRKY) overexpressing tobacco lines. JcWRKY transgenics showed improved photosynthesis rate, stomatal conductance, intercellular CO
concentration/ambient CO
concentration ratio (Ci/Ca ratio), electron transport rate (ETR), photosynthesis efficiency (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (NPQ) and quantum yield of PSII electron transport (ΦPSII) in response to salinity stress, while exogenous SA application had subtle effect on these parameters. Alkane, the major constituent of wax showed maximum accumulation in transgenics exposed to NaCl. Other wax components like fatty alcohol, carboxylic acid and fatty acid were also higher in transgenics with NaCl + SA and SA treatments. Interestingly, the transgenics showed a higher number of open stomata in treated plants as compared to wild type (WT), indicating less perception of stress by the transgenics. Improved salinity tolerance in JcWRKY overexpressing tobacco transgenics is associated with photosynthetic efficiency and wax accumulation, mediated by efficient SA signalling. The transgenics showed differential regulation of genes related to photosynthesis (NtCab40, NtLhcb5 and NtRca1), wax accumulation (NtWIN1) and stomatal regulation (NtMUTE, NtMYB-like, NtNCED3-2 and NtPIF3). The present study indicates that JcWRKY is a potential TF facilitating improved photosynthesis with the wax metabolic co-ordination in transgenics during stress.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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