Improvement of freezing tolerance in tobacco plants expressing a cold-responsive and chloroplast-targeting protein WCOR15 of wheat

Exploring cotton SFR2's conundrum in response to cold stress

Cotton is an important agricultural crop to many regions across the globe but is sensitive to low-temperature exposure. The activity of the enzyme SENSITIVE TO FREEZING 2 (SFR2) improves cold tolerance of plants and produces trigalactosylsyldiacylglycerol (TGDG), but its role in cold sensitive plants, such as cotton remains unknown. Recently, it was reported that cotton SFR2 produced very little TGDG under normal and cold conditions. Here, we investigate cotton SFR2 activation and TGDG production. Using multiple approaches in the native system and transformation into Arabidopsis thaliana, as well as heterologous yeast expression, we provide evidence that cotton SFR2 activates differently than previously found among other plant species. We conclude with the hypothesis that SFR2 in cotton is not activated in a similar manner regarding acidification or freezing like Arabidopsis and that other regions of SFR2 protein are critical for activation of the enzyme than previously reported.

Physiological, molecular, and environmental insights into plant nitrogen uptake, and metabolism under abiotic stresses

Nitrogen (N) as an inorganic macronutrient is inevitable for plant growth, development, and biomass production. Many external factors and stresses, such as acidity, alkalinity, salinity, temperature, oxygen, and rainfall, affect N uptake and metabolism in plants. The uptake of ammonium (NH4 +) and nitrate (NO3 -) in plants mainly depends on soil properties. Under the sufficient availability of NO3 - (>1 mM), low-affinity transport system is activated by gene network NRT1, and under low NO3 - availability (<1 mM), high-affinity transport system starts functioning encoded by NRT2 family of genes. Further, under limited N supply due to edaphic and climatic factors, higher expression of the AtNRT2.4 and AtNRT2.5T genes of the NRT2 family occur and are considered as N remobilizing genes. The NH4 + ion is the final form of N assimilated by cells mediated through the key enzymes glutamine synthetase and glutamate synthase. The WRKY1 is a major transcription factor of the N regulation network in plants. However, the transcriptome and metabolite profiles show variations in N assimilation metabolites, including glycine, glutamine, and aspartate, under abiotic stresses. The overexpression of NO3 - transporters (OsNRT2.3a and OsNRT1.1b) can significantly improve the biomass and yield of various crops. Altering the expression levels of genes could be a valuable tool to improve N metabolism under the challenging conditions of soil and environment, such as unfavorable temperature, drought, salinity, heavy metals, and nutrient stress.

Ectopic expression of StCBF1and ScCBF1 have different functions in response to freezing and drought stresses in Arabidopsis

Solanum tuberosum potato species constitute the bulk of economically and agronomically important potato production. However, S. tuberosum is a drought- and frost-sensitive species that is incapable of acclimating to the cold. Solanum commersonii is a tuber-bearing wild potato species that exhibits greater frost and drought resistance than S. tuberosum. CBF/DREB (C-REPET BINDING FACTOR/DROUGHT RESPONSE ELEMENT BINGING FACTOR) transcription factors play important roles in response to a variety of abiotic stresses, such as cold, drought and salt stresses. To explore different functions between S. tuberosum CBF1 (StCBF1) and S. commersonii CBF1 (ScCBF1), Arabidopsis was transformed with the ScCBF1 and StCBF1 genes driven by a constitutive CaMV35S promoter. Our results reveal that the ScCBF1 transgenic lines are much more tolerant to freezing and drought than the StCBF1 transgenic lines. The development of transgenic plants was altered, resulting in dwarf phenotype with delayed flowering and thicker and additional rosette leaves. The expression levels of several COR (COLD-RESPONSIVE) genes and development-related genes, including genes that inhibited plant growth (GA2ox7, RGL3) and delayed flowering (FLC) were higher in transgenic plants. These results suggest that these two potato CBF1 play important roles in the plant response to abiotic stress and can influence plant growth and development, and ScCBF1 plays a more pronounced function than StCBF1.

iTRAQ and virus-induced gene silencing revealed three proteins involved in cold response in bread wheat

By comparing the differentially accumulated proteins from the derivatives (UC 1110 × PI 610750) in the F₁₀ recombinant inbred line population which differed in cold-tolerance, altogether 223 proteins with significantly altered abundance were identified. The comparison of 10 cold-sensitive descendant lines with 10 cold-tolerant descendant lines identified 140 proteins that showed decreased protein abundance, such as the components of the photosynthesis apparatus and cell-wall metabolism. The identified proteins were classified into the following main groups: protein metabolism, stress/defense, carbohydrate metabolism, lipid metabolism, sulfur metabolism, nitrogen metabolism, RNA metabolism, energy production, cell-wall metabolism, membrane and transportation, and signal transduction. Results of quantitative real-time PCR of 20 differentially accumulated proteins indicated that the transcriptional expression patterns of 10 genes were consistent with their protein expression models. Virus-induced gene silencing of Hsp90, BBI, and REP14 genes indicated that virus-silenced plants subjected to cold stress had more severe drooping and wilting, an increased rate of relative electrolyte leakage, and reduced relative water content compared to viral control plants. Furthermore, ultrastructural changes of virus-silenced plants were destroyed more severely than those of viral control plants. These results indicate that Hsp90, BBI, and REP14 potentially play vital roles in conferring cold tolerance in bread wheat.

Perspective Research Progress in Cold Responses of Capsella bursa-pastoris

Plants respond to cold stress by modulating biochemical pathways and array of molecular events. Plant morphology is also affected by the onset of cold conditions culminating at repression in growth as well as yield reduction. As a preventive measure, cascades of complex signal transduction pathways are employed that permit plants to endure freezing or chilling periods. The signaling pathways and related events are regulated by the plant hormonal activity. Recent investigations have provided a prospective understanding about plant response to cold stress by means of developmental pathways e.g., moderate growth involved in cold tolerance. Cold acclimation assays and bioinformatics analyses have revealed the role of potential transcription factors and expression of genes like CBF, COR in response to low temperature stress. Capsella bursa-pastoris is a considerable model plant system for evolutionary and developmental studies. On different occasions it has been proved that C. bursa-pastoris is more capable of tolerating cold than A. thaliana. But, the mechanism for enhanced low or freezing temperature tolerance is still not clear and demands intensive research. Additionally, identification and validation of cold responsive genes in this candidate plant species is imperative for plant stress physiology and molecular breeding studies to improve cold tolerance in crops. We have analyzed the role of different genes and hormones in regulating plant cold resistance with special reference to C. bursa-pastoris. Review of collected data displays potential ability of Capsella as model plant for improvement in cold stress regulation. Information is summarized on cold stress signaling by hormonal control which highlights the substantial achievements and designate gaps that still happen in our understanding.

Molecular evolution of Wcor15 gene enhanced our understanding of the origin of A, B and D genomes in Triticum aestivum

The allohexaploid bread wheat originally derived from three closely related species with A, B and D genome. Although numerous studies were performed to elucidate its origin and phylogeny, no consensus conclusion has reached. In this study, we cloned and sequenced the genes Wcor15-2A, Wcor15-2B and Wcor15-2D in 23 diploid, 10 tetraploid and 106 hexaploid wheat varieties and analyzed their molecular evolution to reveal the origin of the A, B and D genome in Triticum aestivum. Comparative analyses of sequences in diploid, tetraploid and hexaploid wheats suggest that T. urartu, Ae. speltoides and Ae. tauschii subsp. strangulata are most likely the donors of the Wcor15-2A, Wcor15-2B and Wcor15-2D locus in common wheat, respectively. The Wcor15 genes from subgenomes A and D were very conservative without insertion and deletion of bases during evolution of diploid, tetraploid and hexaploid. Non-coding region of Wcor15-2B gene from B genome might mutate during the first polyploidization from Ae. speltoides to tetraploid wheat, however, no change has occurred for this gene during the second allopolyploidization from tetraploid to hexaploid. Comparison of the Wcor15 gene shed light on understanding of the origin of the A, B and D genome of common wheat.

Extracellular trafficking of a wheat cold-responsive protein, WLT10

A cold-responsive wheat gene, WLT10, encodes a member of the cereal-specific low temperature-responsive/cold-responsive protein family, which contains a hydrophobic N-terminal 20 amino acid sequence that corresponds to signal peptides associated with extracellular trafficking. To verify the subcellular localization of WLT10 and the function of its putative signal peptide, we constructed three chimeric genes in which either the WLT10 signal peptide, a signal peptide with only 6 additional amino acids, or the full-length WLT10 polypeptide was fused to the N-terminus of green fluorescent protein (GFP). These fusion constructs were transiently introduced into onion epidermal cells by particle bombardment. GFP signals were observed not only in the extracellular space (ECS) but also in the endoplasmic reticulum (ER) and Golgi apparatus. The time course of GFP signal localization suggests the movement of WLT10 through the ER/Golgi pathway and into the ECS. Thus, WLT10 is a cold-responsive secreted protein, and its N-terminal 20 amino acid region is important for transport to the ECS.

Comparative proteomic analysis of rd29A:RdreB1BI transgenic and non-transgenic strawberries exposed to low temperature

Low-temperature stress is one of the major abiotic stresses in plants worldwide, and the dehydration responsive element binding protein (DREB) transcription factor induces expression of genes involved in environmental stress tolerance in plants. A proteomic approach based on two-dimensional gel electrophoresis (2-DE) and subsequent mass spectrometric identification was used to study the changes in the leaf proteome profiles of rd29A:RdreB1BI transgenic and non-transgenic strawberries exposed to low-temperature conditions. By comparing the proteomic profiles, we located 21 protein spots that were reproducibly up- or down-regulated by more than twofold between transgenic and non-transgenic strawberries. Eight identified proteins function in energy and metabolism, four in biosynthetic processes, four were stress and defense related, three spots were identified as cold-stress related expressed sequence tags (ESTs), and two were unknown proteins. The change patterns of low-temperature tolerance proteins, including photosynthetic proteins (RuBisCO large subunit and RuBisCO activase), cytoplasmic Cu/Zn-superoxide dismutase (Cu/Zn-SOD), late embryogenesis abundant protein 14-A (Lea14-A), eukaryotic translation initiation factor 5A (eIF5A), and cold-stress related ESTs, were differentially regulated between non-transgenic and rd29A:RdreB1BI transgenic strawberries. They are likely important gene products in the regulatory network of the RdreB1BI gene. Consequently, this study provides the first characterization of the transgenic strawberry proteome and the predicted target proteins of the RdreB1BI gene by using proteomic approaches.

Transgenic tobacco plants over expressing cold regulated protein CbCOR15b from Capsella bursa-pastoris exhibit enhanced cold tolerance

Low temperature is among the most significant abiotic stresses, restricting the habitats of sessile plants and reducing crop productivity. Cold regulated (COR) genes are low temperature-responsive genes expressing under regulation of a specific signal transduction pathway, which is designated C-repeat-binding-factor (CBF) signaling pathway. In the present article, cold bioassay showed that the transcript level of cold regulated gene CbCOR15b from shepherd's purse (Capsella bursa-pastoris) was obviously elevated under cold treatments. Reverse transcription-PCR (RT-PCR) and GUS report system revealed that unlike AtCOR15b, CbCOR15b expressed not only in leaves but also in stems and maturation zone of roots. When transgenic tobacco plants ectopically expressing CbCOR15b were exposed to chilling and freezing temperatures, they displayed more cold tolerance compared to control plants. According to the electrolyte leakage, the relative water content, the glucose content and the phenotype observation, CbCOR15b transformants suffered less damage under cold stress. Further investigation of the subcellular localization of CbCOR15b by transient expression of fusion protein CbCOR15b-GFP revealed that it was localized exclusively in the chloroplasts of tobacco mesophyll cells and in the cytoplasm of onion epidermal cells. It can be concluded that CbCOR15b which located in the chloroplasts and in the cytoplasm of cells without chloroplasts was involved in cold response of C. bursa-pastoris and conferred enhanced cold tolerance in transgenic tobacco plants.

A LEA gene regulates Cadmium tolerance by mediating physiological responses

In this study, the function of a LEA gene (TaLEA1) from Tamrix androssowii in response to heavy metal stress was characterized. Time-course expression analyses showed that NaCl, ZnCl₂, CuSO₄, and CdCl₂ considerably increased the expression levels of the TaLEA1 gene, thereby suggesting that this gene plays a role in the responses to these test stressors. To analyze the heavy metal stress-tolerance mechanism regulated by TaLEA1, TaLEA1-overexpressing transgenic poplar plants (Populus davidiana Dode × P. bollena Lauche) were generated. Significant differences were not observed between the proline content of the transgenic and wild-type (WT) plants before and after CdCl₂ stress. However, in comparison with the WT plants, the TaLEA1-transformed poplar plants had significantly higher superoxide dismutase (SOD) and peroxidase (POD) activities, and lower malondialdehyde (MDA) levels under CdCl₂ stress. Further, the transgenic plants showed better growth than the WT plants did, indicating that TaLEA1 provides tolerance to cadmium stress. These results suggest that TaLEA1 confers tolerance to cadmium stress by enhancing reactive oxygen species (ROS)-scavenging ability and decreasing lipid peroxidation. Subcellular-localization analysis showed that the TaLEA1 protein was distributed in the cytoplasm and nucleus.

Expression analysis and functional characterization of a novel cold-responsive gene CbCOR15a from Capsella bursa-pastoris

The cold-responsive (COR) genes involved in C-repeat binding factor signaling pathway function essentially in cold acclimation of higher plants. A novel COR gene CbCOR15a from shepherd's purse (Capsella bursa-pastoris) was predicted to be a homolog of COR15 in Arabidopsis. The analysis of tissue specific expression pattern as well as characterization of the CbCOR15a promoter revealed that the expression of CbCOR15a was induced by coldness not only in leaves and stem but also in roots. Sequence analysis showed that a 909 bp promoter region of CbCOR15a contained two CRT/DRE elements, two ABRE elements, one auxin-responsive TGA-element and one MeJA-responsive CGTCA-motif. In young seedlings the expression of CbCOR15a could be apparently increased by SA, ABA, MeJA and IAA, and transiently increased by GA(3) accompanied by obvious feedback suppression. According to the altered physiological index values in tobacco under cold treatments, the overexpression of CbCOR15a significantly increased the cold tolerance of transgenic tobacco plants. It can be suggested that CbCOR15a was involved in cold response of Capsella bursa-pastoris associated with SA, ABA, MeJA, IAA and GA(3) regulation and confers enhanced cold acclimation in transgenic plants.

Role of transgenic plants in agriculture and biopharming

At present, environmental degradation and the consistently growing population are two main problems on the planet earth. Fulfilling the needs of this growing population is quite difficult from the limited arable land available on the globe. Although there are legal, social and political barriers to the utilization of biotechnology, advances in this field have substantially improved agriculture and human life to a great extent. One of the vital tools of biotechnology is genetic engineering (GE) which is used to modify plants, animals and microorganisms according to desired needs. In fact, genetic engineering facilitates the transfer of desired characteristics into other plants which is not possible through conventional plant breeding. A variety of crops have been engineered for enhanced resistance to a multitude of stresses such as herbicides, insecticides, viruses and a combination of biotic and abiotic stresses in different crops including rice, mustard, maize, potato, tomato, etc. Apart from the use of GE in agriculture, it is being extensively employed to modify the plants for enhanced production of vaccines, hormones, etc. Vaccines against certain diseases are certainly available in the market, but most of them are very costly. Developing countries cannot afford the disease control through such cost-intensive vaccines. Alternatively, efforts are being made to produce edible vaccines which are cheap and have many advantages over the commercialized vaccines. Transgenic plants generated for this purpose are capable of expressing recombinant proteins including viral and bacterial antigens and antibodies. Common food plants like banana, tomato, rice, carrot, etc. have been used to produce vaccines against certain diseases like hepatitis B, cholera, HIV, etc. Thus, the up- and down-regulation of desired genes which are used for the modification of plants have a marked role in the improvement of genetic crops. In this review, we have comprehensively discussed the role of genetic engineering in generating transgenic lines/cultivars of different crops with improved nutrient quality, biofuel production, enhanced production of vaccines and antibodies, increased resistance against insects, herbicides, diseases and abiotic stresses as well as the safety measures for their commercialization.

A novel cold-regulated gene, COR25, of Brassica napus is involved in plant response and tolerance to cold stress

Cold stress, which causes dehydration damage to the plant cell, is one of the most common abiotic stresses that adversely affect plant growth and crop productivity. To improve its cold-tolerance, plants often enhance expression of some cold-related genes. In this study, a cold-regulated gene encoding 25 KDa of protein was isolated from Brassica napus cDNA library using a macroarray analysis, and is consequently designated as BnCOR25. RT-PCR analysis demonstrated that BnCOR25 was expressed at high levels in hypocotyls, cotyledons, stems, and flowers, but its mRNA was found at low levels in roots and leaves. Northern blot analysis revealed that BnCOR25 transcripts were significantly induced by cold and osmotic stress treatment. The data also showed that BnCOR25 gene expression is mediated by ABA-dependent pathway. Overexpression of BnCOR25 in yeast (Schizosaccharomyces pombe) significantly enhanced the cell survival probability under cold stress, and overexpression of BnCOR25 in Arabidopsis enhances plant tolerance to cold stress. These results suggested that the BnCOR25 gene may play an important role in conferring freezing/cold tolerance in plants.

A DREB gene from Limonium bicolor mediates molecular and physiological responses to copper stress in transgenic tobacco

The DRE-binding (DREB) transcription factors play an important role in regulating stress-related genes. In the present study, a novel DREB gene (LbDREB) from Limonium bicolor was cloned. To characterize the function of DREB in heavy metal stress tolerance, LbDREB-transformed tobacco plants were generated and subjected to CuSO(4) stress. Analysis of the role of LbDREB in tolerance to copper stress in transgenic tobacco showed that overexpression of LbDREB increased the contents of soluble protein and proline, and elevated the ratio of K to Na under CuSO(4) stress. Moreover, overexpression of LbDREB can up-regulate some stress-related genes, including Cu/Zn superoxide dismutase (Cu/Zn SOD), peroxidases (PODs), late embryogenesis abundant (LEA), and lipid transfer proteins (LTP). These results suggest that LbDREB can enhance plant copper tolerance by up-regulating a series of stress-related genes, thereby mediating physiological processes associated with stress tolerance in plants.

CBF-dependent signaling pathway: a key responder to low temperature stress in plants

Plants under low temperature (LT) stress exhibit a C-repeat binding factor (CBF)-dependent responsive pathway. The transcription factors in the CBF family, existing in multiple plant species, are the key regulators of the cold-responsive (COR) genes. CBF1 and CBF3 are regulated in a different way from CBF2, and CBF4 is the only known CBF gene definitely involved in abscisic acid (ABA)-dependent signaling pathways. RAP2.1 and RAP2.6 are the downstream regulators under CBFs. The upstream regulators of the CBF named inducer of CBF expression (ICE) acts as a positive regulator of CBFs. Meanwhile, these CBF signaling pathway components could associate with many other transcription activators and repressors in regulating gene expression when plants are under LT stress. HOS1 negatively regulates ICE1, which down regulates MYB15, an upstream repressor of CBFs. ZAT12 participates in the repression of CBFs, while ZAT10 and FRY2 negatively regulate the CBF-target genes. ADF5 was recently also found to repress CBFs. LOS2 works against ZAT10, and LOS4 positively regulates CBFs. SFR6 is involved in the modification of CBFs to activate the COR genes, and SIZ1-dependent sumoylation plays a positive role in the regulation of ICE1. The utilization of CBF-dependent signaling components has a broad perspective in the field of plant breeding for enhancing crop LT tolerance.

Overexpression of PgDREB2A transcription factor enhances abiotic stress tolerance and activates downstream stress-responsive genes

The DREB transcription factors comprise conserved ERF/AP2 DNA-binding domain, bind specifically to DRE/CRT motif and regulate abiotic stress mediated gene expression. In this study we show that PgDREB2A from Pennisetum glaucum is a powerful transcription factor to engineer multiple stress tolerance in tobacco plants. The PgDREB2A protein lacks any potential PEST sequence, which is known to act as a signal peptide for protein degradation. Therefore, the transgenic tobacco plants were raised using full-length cDNA without modification. The transgenics exhibited enhanced tolerance to both hyperionic and hyperosmotic stresses. At lower concentration of NaCl and mannitol, seed germination and seedling growth was similar in WT and transgenic, however at higher concentration germination in WT decreased significantly. D15 and D46 lines showed 4-fold higher germination percent at 200 mM NaCl. At 400 mM mannitol seed germination in WT was completely arrested, whereas in transgenic line it was more than 50%. Seedlings of D15 and D46 lines showed better growth like leaf area, root number, root length and fresh weight compared to wild type for both the stresses. The quantitative Real time PCR of transgenic showed higher expression of downstream genes NtERD10B, HSP70-3, Hsp18p, PLC3, AP2 domain TF, THT1, LTP1 and heat shock (NtHSF2) and pathogen-regulated (NtERF5) factors with different stress treatments.

Effects of molybdenum on expression of cold-responsive genes in abscisic acid (ABA)-dependent and ABA-independent pathways in winter wheat under low-temperature stress

BACKGROUND AND AIMS

Molybdenum (Mo) is an essential trace element for higher plants. It has been shown that application of Mo enhances the cold resistance of winter wheat. In order to improve our understanding of the molecular mechanisms of cold resistance arising from application of Mo in winter wheat, investigations were made regarding the transcription of cold-responsive (COR) genes in abscisic acid (ABA)-dependent and ABA-independent pathways in winter wheat regulated by Mo application under low-temperature stress.

METHODS

Two cultivars of winter wheat (Triticum aestivum), Mo-efficient cultivar '97003' and Mo-inefficient cultivar '97014', were grown in control (-Mo) and Mo fertilizer (+Mo) treatments for 40 d at 15/12 degrees C (day/night), and the temperature was then reduced to 5/2 degrees C (day/night) to create low-temperature stress. Aldehyde oxidase (AO) activities, ABA contents, the transcripts of basic leucine zipper (bZIP)-type transcription factor (TF) genes, ABA-dependent COR genes, CBF/DREB transcription factor genes and ABA-independent COR genes were investigated at 0, 3, 6 and 48 h post cold stress.

KEY RESULTS

Mo application significantly increased AO activity, ABA levels, and expression of bZIP-type TF genes (Wlip19 and Wabi5) and ABA-dependent COR genes (Wrab15, Wrab17, Wrab18 and Wrab19). Mo application increased expression levels of CBF/DREB transcription factor genes (TaCBF and Wcbf2-1) and ABA-independent COR genes (Wcs120, Wcs19, Wcor14 and Wcor15) after 3 and 6 h exposure to low temperature.

CONCLUSIONS

Mo might regulate the expression of ABA-dependent COR genes through the pathway: Mo --> AO --> ABA --> bZIP --> ABA-dependent COR genes in winter wheat. The response of the ABA-dependent pathway to Mo was prior to that of the ABA-independent pathway. Similarities and differences between the Mo-efficient and Mo-inefficient wheat cultivars in response to Mo under cold stress are discussed.

How plants cope with cadmium: staking all on metabolism and gene expression

Environmental pollution is one of the major problems for human health. Toxic heavy metals are normally present as soil constituents or can also be spread out in the environment by human activity and agricultural techniques. Soil contamination by heavy metals as cadmium, highlights two main aspects: on one side they interfere with the life cycle of plants and therefore reduce crop yields, and on the other hand, once adsorbed and accumulated into the plant tissues, they enter the food chain poisoning animals and humans. Considering this point of view, understanding the mechanism by which plants handle heavy metal exposure, in particular cadmium stress, is a primary goal of plant-biotechnology research or plant breeders whose aim is to create plants that are able to recover high amounts of heavy metals, which can be used for phytoremediation, or identify crop varieties that do not accumulate toxic metal in grains or fruits. In this review we focus on the main symptoms of cadmium toxicity both on root apparatus and shoots. We elucidate the mechanisms that plants activate to prevent absorption or to detoxify toxic metal ions, such as synthesis of phytochelatins, metallothioneins and enzymes involved in stress response. Finally we consider new plant-biotechnology applications that can be applied for phytoremediation.

Increased freezing tolerance through up-regulation of downstream genes via the wheat CBF gene in transgenic tobacco

The wheat (Triticum aestivum L.) CBF gene family is assumed to play important roles in development of low-temperature and freezing tolerance through activation of the downstream Cor/Lea genes. However, no direct evidence shows association of the wheat CBF genes with stress tolerance or any interaction between wheat CBF transcription factors and Cor/Lea gene activation. Here, we introduced Wcbf2, one of the wheat CBF genes, into the tobacco (Nicotiana tabacum L.) genome. Expression of Wcbf2 significantly increased the level of freezing tolerance in the transgenic tobacco plants without phenotypic retardation, and altered the expression patterns of tobacco genes, including cold-responsive genes. A transgenic tobacco plant expressing Wcbf2 was crossed to other transgenic plants expressing a GUS reporter gene under control of the wheat Cor/Lea gene promoter. Analysis of the F(1) plants showed that the WCBF2 protein positively regulated at least the expression of Wdhn13 and Wrab17. These results strongly indicate that WCBF2 functions as a transcription factor in the development of freezing tolerance in common wheat.

Role of DREB transcription factors in abiotic and biotic stress tolerance in plants

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.

Real-time GUS analysis using Q-PCR instrumentation

The development of new technology within biological sciences has resulted in a number of real-time PCR instruments that have become essential tools within molecular biology. This equipment has facilitated high throughput analysis of samples and optimal information gathering of completed PCR reactions for example estimating the copy number of a gene of interest that is inserted into particular genomes. Real-time PCR instruments frequently come with optional filter sets, e.g. the ALEXA filter set which has parameters in common with excitation and emission wavelengths of sodium methyl umbelliferone (NaMU) widely used in beta-glucuronidase reporter gene assays. Using these filter sets it has been possible to quantify and measure gus A activity of Ulmus procera SR4 in real-time removing the necessity for aliquots of reactions to be stopped by pipetting into carbonate buffer for each time point. The introduction of real-time GUS analysis leads to faster, more accurate and reproducible assays with reduced potential for pipetting errors, requires fewer manipulations and encourages high throughput analysis of inter-individual gene expression variation.