Overexpression of KcNHX1 gene confers tolerance to multiple abiotic stresses in Arabidopsis thaliana

Journal of Plant Research - Abiotic stresses such as drought, salinity, and heat affect plant growth and development. Karelinia caspica is a unique perennial herb that grows in desert area for a...     

Two poplar calcineurin B-like proteins confer enhanced tolerance to abiotic stresses in transgenic Arabidopsis thaliana

Calcium is a critical component in a number of plant signal transduction pathways and the calcineurin B-like protein (CBL) family is a unique group of calcium sensors regulating a family of CBL-interacting protein kinases (CIPKs). In this study, two poplar CBL genes, PeCBL6 (GenBank acc. No. DQ907710) and PeCBL10 (GenBank acc. No. DQ899956), were characterized in transgenic Arabidopsis thaliana, particularly with regard to its role in abiotic stress resistance. Expression of the two CBL genes in poplar was induced by cold, drought, or high salinity, but not by abscisic acid (ABA) treatment. In Arabidopsis thaliana, PeCBL6 was found in the nucleus and PeCBL10 in the tonoplast. Transgenic Arabidopsis plants overexpressing PeCBL6 or PeCBL10 showed enhanced tolerance to high salinity, drought and low temperature. These results suggested that PeCBL6 and PeCBL10 may function as positive regulators of salt, drought and temperature responses.     

Constitutive expression of a meiotic recombination protein gene homolog, OsTOP6A1, from rice confers abiotic stress tolerance in transgenic Arabidopsis plants

Plant productivity is greatly influenced by various environmental stresses, such as high salinity and drought. Earlier, we reported the isolation of topoisomerase 6 homologs from rice and showed that over expression of OsTOP6A3 and OsTOP6B confers abiotic stress tolerance in transgenic Arabidopsis plants. In this study, we have assessed the function of nuclear-localized topoisomerase 6 subunit A homolog, OsTOP6A1, in transgenic Arabidopsis plants. The over expression of OsTOP6A1 in transgenic Arabidopsis plants driven by cauliflower mosaic virus-35S promoter resulted in pleiotropic effects on plant growth and development. The transgenic Arabidopsis plants showed reduced sensitivity to stress hormone, abscisic acid (ABA), and tolerance to high salinity and dehydration at the seed germination; seedling and adult stages as reflected by the percentage of germination, fresh weight of seedlings and leaf senescence assay, respectively. Concomitantly, the expression of many stress-responsive genes was enhanced under various stress conditions in transgenic Arabidopsis plants. Moreover, microarray analysis revealed that the expression of a large number of genes involved in various processes of plant growth and development and stress responses was altered in transgenic plants. Although AtSPO11-1, the homolog of OsTOP6A1 in Arabidopsis, has been implicated in meiotic recombination; the present study demonstrates possible additional role of OsTOP6A1 and provides an effective tool for engineering crop plants for tolerance to different environmental stresses. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Enhanced ascorbic acid accumulation in transgenic potato confers tolerance to various abiotic stresses

l-Ascorbic acid (Vitamin C, AsA) is an important component of human nutrition. Plants and several animals can synthesize their own ascorbic acid, whereas humans lack the gene essential for ascorbic acid biosynthesis and must acquire from their diet. In the present study, we developed transgenic potato (Solanum tuberosum L. cv. Taedong Valley) over-expressing l-gulono-γ-lactone oxidase (GLOase gene; NCBI Acc. No. NM022220), isolated from rat cells driven by CaMV35S constitutive promoter that showed enhanced AsA accumulation. Molecular analyses of four independent transgenic lines performed by PCR, Southern and RT-PCR revealed the stable integration of the transgene in the progeny. The transformation frequency was ca. 7.5% and the time required for the generation of transgenic plants was 6–7 weeks. Transgenic tubers showed significantly enhanced AsA content (141%) and GLOase activity as compared to untransformed tubers. These transgenics were also found to withstand various abiotic stresses caused by Methyl Viologen (MV), NaCl or mannitol, respectively. The T₁ transgenic plants exposed to salt stress (100 mM NaCl) survived better with increased shoot and root length when compared to untransformed plants. The elevated level of AsA accumulation in transgenics was directly correlated with their ability to withstand abiotic stresses. These results further demonstrated that the overexpression of GLOase gene enhanced basal levels of AsA in potato tubers and also the transgenics showed better survival under various abiotic stresses.     

LlDREB1G,a novel DREB subfamily gene from Lilium longiflorum,can enhance transgenic Arabidopsis tolerance to multiple abiotic stresses

Plant Cell, Tissue and Organ Culture (PCTOC) - Suspension-cultured Dracocephlum polychaetum Bornm. is a wild medicinal herb native to Iran, treated with a static magnetic field (SMF) and Fe2O3...     

Glutathione peroxidase-like protein of Synechocystis PCC 6803 confers tolerance to oxidative and environmental stresses in transgenic Arabidopsis

Glutathione peroxidase (GPX)-like proteins (GPX-1 and GPX-2) of Synechocystis PCC 6803 ( S. PCC 6803) reduce unsaturated fatty acid hydroperoxides using NADPH, but not reduced glutathione (GSH), as an electron donor. Here, we generated transgenic Arabidopsis plants overexpressing S. PCC 6803 GPX-2 in the cytosol (AcGPX2) or chloroplasts (ApGPX2). The activities toward α-linolenic acid hydroperoxide in ApGPX2 and AcGPX2 plants were 6.5–11.5 and 8.2–16.3 nmol min⁻¹ mg protein⁻¹, respectively, while no activity (<0.1 nmol min⁻¹ mg protein⁻¹) was detected in the wild-type plants. Both transgenic lines (AcGPX2 and ApGPX2) showed enhanced tolerance to oxidative damage caused by treatment with H₂O₂ (10 m M ), Fe ions (200 μ M ) or methylviologen (50 μ M ) and environmental stress conditions, such as chilling with high light intensity (4°C, 1000 μmol photons m⁻² s⁻¹), high salinity (100 m M NaCl) or drought. The degree of tolerance of the transgenic plants to all types of stress was correlated with the levels of lipid peroxide suppressed by the overexpression of S. PCC 6803 GPX-2. Under conditions of oxidative stress due to the H₂O₂ treatment, the NADPH/(NADP⁺+ NADPH) ratio in the transgenic plants was lower than that in the wild-type plants. The data reported here indicate that the expression of S. PCC 6803 GPX-2 contributes to the reduction in unsaturated fatty acid hydroperoxides using NADPH in situ under stress conditions in the transgenic plants.     

RcLEA,a late embryogenesis abundant protein gene isolated from Rosa chinensis,confers tolerance to Escherichia coli and Arabidopsis thaliana and stabilizes enzyme activity under diverse stresses

The late embryogenesis abundant (LEA) protein family is a large protein family that is closely associated with resistance to abiotic stresses in many organisms, such as plants, bacteria and animals. In this study, we isolated a LEA gene, RcLEA, which was cytoplasm-localized, from Rosa chinensis. RcLEA was found to be induced by high temperature through RT-PCR. Overexpression of RcLEA in Escherichia coli improved its growth performance compared with the control under high temperature, low temperature, NaCl and oxidative stress conditions. RcLEA was also overexpressed in Arabidopsis thaliana. The transgenic Arabidopsis showed better growth after high and low temperature treatment and exhibited less peroxide according to 3, 3-diaminobenzidine staining. However, RcLEA did not improve the tolerance to NaCl or osmotic stress in Arabidopsis. In vitro analysis showed that RcLEA was able to prevent the freeze–thaw-induced inactivation or heat-induced aggregation of various substrates, such as lactate dehydrogenase and citrate synthase. It also protected the proteome of E. coli from denaturation when the proteins were heat-shocked or subjected to acidic conditions. Furthermore, bimolecular fluorescence complementation assays suggested that RcLEA proteins function in a complex manner by making the form of homodimers.     

Combinational transformation of three wheat genes encoding fructan biosynthesis enzymes confers increased fructan content and tolerance to abiotic stresses in tobacco

Key message

Seven kinds of transgenic tobacco plants transformed with combinations of three FBE genes were obtained. The transgenic plants transformed with Ta1-SST?+?Ta6-SFT genes appeared to have the highest fructan or soluble sugar content and the strongest salt tolerance.

Abstract

Fructan is thought to be one of the important regulators involved in plant tolerance to various abiotic stresses. In this study, wheat-derived genes, Ta1-SST, Ta6-SFT, and Ta1-FFT, encoding fructan biosynthesis enzymes (FBE) were isolated and cloned into vectors modified pBI121 or pZP211. Seven different combinations of the three target genes were transformed into tobacco plants through an Agrobacterium-mediated approach, and transgenic tobacco plants were identified by PCR, ELISA, and Southern blotting. Compared with tobacco plants transformed with other six combinations of the three target genes and with wild-type plants, the transgenic plants transformed with Ta1-SST?+?Ta6-SFT genes contained the highest fructan and soluble sugar content. All seven types of transgenic tobacco plants displayed a much higher level of tolerance to drought, low temperature, and high salinity compared with the wild type. Differences of drought and low temperature tolerance between the transgenic plants containing a single FBE gene and those harboring two or three FBE genes were not significant, but the salt tolerance level of the transgenic plants with different FBE gene combinations from high to low was: Ta1-SST?+?Ta6-SFT?>?Ta1-SST?+?Ta6-SFT?+?Ta1-FFT?>?Ta1-SST?+?Ta1-FFT?>?Ta1-SFT?+?Ta1-FFT?>?single FBE gene. These results indicated that the tolerances of the transgenic tobacco plants to various abiotic stresses were associated with the transformed target gene combinations and the contents of fructan and soluble sugar contained in the transgenic plants.     

Overexpression of a rice gene encoding a small C2 domain protein OsSMCP1 increases tolerance to abiotic and biotic stresses in transgenic Arabidopsis

Plant growth and crop production are limited by environmental stress. We used a large population of transgenic Arabidopsis expressing rice full-length cDNAs to isolate the rice genes that improve the tolerance of plants to environmental stress. By sowing T2 seeds of the transgenic lines under conditions of salinity stress, the salt-tolerant line R07047 was isolated. It expressed a rice gene, OsSMCP1, which encodes a small protein with a single C2 domain, a Ca²⁺-dependent membrane-targeting domain. Retransformation of wild-type Arabidopsis revealed that OsSMCP1 is responsible for conferring the salt tolerance. It is particularly interesting that R07047 and newly constructed OsSMCP1-overexpressing Arabidopsis showed enhanced tolerance not only to high salinity but also to osmotic, dehydrative, and oxidative stresses. Furthermore, R07047 showed improved resistance to Pseudomonas syringae. The OsSMCP1 expression in rice is constitutive. Particle-bombardment-mediated transient expression analysis revealed that OsSMCP1 is targeted to plastids in rice epidermal cells. It induced overexpression of several nuclear encoded genes, including the stress-associated genes, in transgenic Arabidopsis. No marked morphological change or growth retardation was observed in R07047 or retransformants. For molecular breeding to improve the tolerance of crops against environmental stress, OsSMCP1 is a promising candidate.     

The arabinose kinase,ARA1, gene of Arabidopsis is a novel member of the galactose kinase gene family

The arabinose-sensitive ara1-1 mutant of Arabidopsis is deficient in arabinose kinase activity. A candidate for the ARA1 gene, ISA1, has been previously identified through the Arabidopsis genome sequencing initiative. Here we demonstrate that (1) the ARA1 gene coincides with ISA1 in a positional cloning strategy; (2) there are mutations in the ISA1 gene in both the ara1-1 mutant and an intragenic suppressor mutant; and (3) the ara1-1 and suppressor mutant phenotypes can be complemented by the expression of the ISA1 cDNA in transgenic plants. Together these observations confirm that ISA1 is the ARA1 gene. ARA1 is a member of the galactose kinase family of genes and represents a new substrate specificity among this and other families of sugar kinases. A second gene with similarities to members of the galactose kinase gene family has been identified in the EST database. A 1.8 kb cDNA contained an open reading-frame predicted to encode a 496 amino acid polypeptide. The GAL1 cDNA was expressed in a galK mutant of Escherichia coli and in vitro assays of extracts of the strain expressing GAL1 confirmed that the cDNA encodes a galactose kinase activity. Both GAL1 and ARA1 cross-hybridise at low stringency to other sequences suggesting the presence of additional members of the galactose kinase gene family.     

Chilling tolerance in Arabidopsis involves ALA1, a member of a new family of putative aminophospholipid translocases

The lipid composition of membranes is a key determinant for cold tolerance, and enzymes that modify membrane structure seem to be important for low-temperature acclimation. We have characterized ALA1 (for aminophospholipid ATPase1), a novel P-type ATPase in Arabidopsis that belongs to the gene family ALA1 to ALA11. The deduced amino acid sequence of ALA1 is homologous with those of yeast DRS2 and bovine ATPase II, both of which are putative aminophospholipid translocases. ALA1 complements the deficiency in phosphatidylserine internalization into intact cells that is exhibited by the drs2 yeast mutant, and expression of ALA1 results in increased translocation of aminophospholipids in reconstituted yeast membrane vesicles. These lines of evidence suggest that ALA1 is involved in generating membrane lipid asymmetry and probably encodes an aminophospholipid translocase. ALA1 complements the cold sensitivity of the drs2 yeast mutant. Downregulation of ALA1 in Arabidopsis results in cold-affected plants that are much smaller than those of the wild type. These data suggest a link between regulation of transmembrane bilayer lipid asymmetry and the adaptation of plants to cold.