Overexpression of a ItICE1 gene from Isatis tinctoria enhances cold tolerance in rice

ItICE1, a ICE1-like gene, was isolated from a cDNA library from cold-treated woad (Isatis tinctoria L.) tissues. Expression analysis revealed that the ItICE1 gene was expressed constitutively and was predominant in the leaves of woad seedlings and that its mRNA accumulation was altered by salt stress and abscisic acid application, but not by dehydration and cold stresses. The transgenic rice lines overexpressing ItICE1 showed no growth retardation under normal growth conditions as well as enhanced tolerance to cold stress. Physiological assays showed that ItICE1 not only increased the accumulation of free proline and chlorophyll in transgenic rice lines under cold stress, but also reduced malondialdehyde content and electrolyte leakage. The analysis of gene expression in transgenic rice lines indicated that the maize ubiquitin promoter could respond to cold stress and upregulate ItICE1 gene expression level under its control. Under cold stress conditions, transgenic lines had a remarkably increased expression of OsDREB1A, J013078A14, 001-125-G03, 001-023-B08 and J023042N13 compared to wild-type plants (P < 0.05), implying that ItICE1 functions in the CBF/DREB1 cold-response pathway. These results demonstrate that ItICE1 plays an important regulatory role in the improvement of tolerance to cold stress in rice and is potentially useful for improving the cold tolerance of other plants.     

Overexpression of OsHsp17.0 and OsHsp23.7 enhances drought and salt tolerance in rice

Heat shock proteins (Hsps) play an important role in plant stress tolerance. We previously reported that expression of OsHsp17.0 and OsHsp23.7 could be enhanced by heat shock treatment and/or other abiotic stresses. In this paper, stress tolerance assays of transgenic rice plants overexpressing OsHsp17.0 and OsHsp23.7 have been carried out. Both OsHsp17.0-OE and OsHsp23.7-OE transgenic lines demonstrated higher germination ability compared to wild-type (WT) plants when subjected to mannitol and NaCl. Phenotypic analysis showed that transgenic rice lines displayed a higher tolerance to drought and salt stress compared to WT plants. In addition, transgenic rice lines showed significantly lower REC, lower MDA content and higher free proline content than WT under drought and salt stresses. These results suggest that OsHsp17.0 and OsHsp23.7 play an important role in rice acclimation to salt and drought stresses and are useful for engineering drought and salt tolerance rice.     

Overexpression of a tobacco osmotin gene in carrot (Daucus carota L.) enhances drought tolerance

Osmotin and osmotin-like proteins belong to the PR-5 pathogenesis-related group of proteins and are induced in response to various types of biotic and abiotic stresses in several plant species. Carrot was transformed with a tobacco osmotin gene that encodes a protein lacking the vacuolar-sorting motif that is composed of a 20-amino-acid sequence at the C-terminal end, under the control of the cauliflower mosaic virus 35S promoter, using Agrobacterium-mediated transformation. Transgene integration and expression were confirmed by Southern and western blot analyses, and three selected transgenic lines were evaluated for their ability to tolerate drought stress. Under drought stress conditions, all transformants exhibited slower rates of wilting compared with the wild-type plants and recovered faster when the drought stress was alleviated. Transformants showed lower levels of hydrogen peroxide accumulation, reduced lipid peroxidation and electrolyte leakage, and higher leaf water content under drought stress. Our results provide additional evidence for the protective ability of the osmotin protein against drought stress conditions and suggest a possible means to achieve tolerance against this abiotic stress in plants.     

Overexpression of a TFIIIA-type zinc finger protein gene ZFP252 enhances drought and salt tolerance in rice (Oryza sativa L.)

We previously identified a salt and drought stress-responsive TFIIIA-type zinc finger protein gene ZFP252 from rice. Here we report the functional analysis of ZFP252 using gain- and loss-of-function strategies. We found that overexpression of ZFP252 in rice increased the amount of free proline and soluble sugars, elevated the expression of stress defense genes and enhanced rice tolerance to salt and drought stresses, as compared with ZFP252 antisense and non-transgenic plants. Our findings suggest that ZFP252 plays an important role in rice response to salt and drought stresses and is useful in engineering crop plants with enhanced tolerance to salt and drought stresses.     

Overexpression of Os2H16 enhances resistance to phytopathogens and tolerance to drought stress in rice

Os2H16, a rice gene of unknown function, has been previously reported to be upregulated in response to infection by Xanthomonas oryzae pv. oryzae. In this study, expression patterns of Os2H16 were analyzed, demonstrating that expression of Os2H16 was dramatically induced by both bacterial and fungal infection as well as by drought stress, but repressed by salt treatment. To further investigate the role of Os2H16 in plant defense responses to abiotic and biotic stresses, transgenic lines of rice were developed. In comparison with wild-type rice, transgenic lines overexpressing Os2H16 show enhanced tolerance to bacterial blight and sheath blight disease, respectively caused by Xanthomonas oryzae pv. oryzae and Rhizoctonia solani. On the contrary, Os2H16 knockdown lines were more susceptible to both pathogens. Consistent with their individual phenotypes, upon inoculation, the expression of defense-related marker genes were elevated in Os2H16 overexpression individuals than in wild-type, while they were significantly reduced in Os2H16 knockdown lines. We also show that Os2H16 overexpression lines display enhanced tolerance to drought stress and elevated induction of drought-related genes, compared to wild-type rice. Os2H16 knockdown lines were more sensitive to drought stress and exhibited reduced induction of drought-related genes. Our study provides the first functional characterization of the rice Os2H16 gene, and suggests that Os2H16 positively modulate plant defense to abiotic and biotic stress.     

Overexpression of PtAnnexin1 from Populus trichocarpa enhances salt and drought tolerance in transgenic poplars

Tree Genetics & Genomes - High numbers of endemic plants exist in subtropical China, but there have been few investigations of the phylogeography and dynamic history for endemic tree species in...     

Overexpression of the Arabidopsis AtEm6 gene enhances salt tolerance in transgenic rice cell lines

The Arabidopsis thaliana late embryogenesis abundant gene AtEm6 is required for normal seed development and for buffering the rate of dehydration during the latter stages of seed maturation. However, its function in salt stress tolerance is not fully understood. In this investigation, cell suspension cultures of three plant species rice (Oryza sativa L.), cotton (Gossypium hirsutum L.), and white pine (Pinus strobes L.) were transformed using Agrobacterium tumefaciens strain LBA4404 harboring pBI-AtEm6. Integration of the AtEm6 gene into the genome of rice, cotton, and white pine has been confirmed by polymerase chain reaction, Southern blotting, and northern blotting analyses. Three transgenic cell lines from each of O. sativa, G. hirsutum, and P. strobus were used to analyze salt stress tolerance conferred by the overexpression of the AtEm6 gene. Our results demonstrated that expression of the AtEm6 gene enhanced salt tolerance in transgenic cell lines. A decrease in lipid peroxidation and an increment in antioxidant enzymes ascorbate peroxidase, glutathione reductase and superoxide dismutase activities were observed in the transgenic cell lines, compared to the non- transgenic control. In rice, AtEM6 increased expression of Ca²⁺-dependent protein kinase genes OsCPK6, OsCPK9, OsCPK10, OsCPK19, OsCPK25, and OsCPK26 under treatment of salt. These results suggested that overexpression of the AtEM6 gene in transgenic cell lines improved salt stress tolerance by regulating expression of Ca²⁺-dependent protein kinase genes. Overexpression of the AtEM6 gene could be an alternative choice for engineering plant abiotic stress tolerance.     

Overexpression of a rice diacylglycerol kinase gene OsBIDK1 enhances disease resistance in transgenic tobacco

A rice diacylglycerol kinase (DGK) gene, OsBIDK1, which encodes a 499-amino acid protein, was cloned and characterized. OsBIDK1 contains a conserved DGK domain, consisting of a diacylglycerol kinase catalytic subdomain and a diacylglycerol kinase accessory subdomain. Expression of OsBIDK1 in rice seedlings was induced by treatment with benzothiadiazole (BTH), a chemical activator of the plant defense response, and by infection with Magnaporthe grisea, causal agent of blast disease. In BTH-treated rice seedlings, expression of OsBIDK1 was induced earlier and at a higher level than in water-treated control seedlings after inoculation with M. grisea. Transgenic tobacco plants that constitutively express the OsBIDK1 gene were generated and disease resistance assays showed that overexpression of OsBIDK1 in transgenic tobacco plants resulted in enhanced resistance against infection by tobacco mosaic virus and Phytophthora parasitica var. nicotianae. These results suggest that OsBIDK1 may play a role in disease resistance responses.     

Overexpression of Arabidopsis translationally controlled tumor protein gene AtTCTP enhances drought tolerance with rapid ABA-induced stomatal closure

Translationally controlled tumor protein (TCTP), also termed P23 in human, belongs to a family of calcium- and tubulin-binding proteins, and it is generally regarded as a growth-regulating protein. Recently, Arabidopsis TCTP (AtTCTP) has been reported to function as an important growth regulator in plants. On the other hand, plant TCTP has been suggested to be involved in abiotic stress signaling such as aluminum, salt, and water deficit by a number of microarray or proteomic analyses. In this study, the biological functions of AtTCTP were investigated by using transgenic Arabidopsis plants overexpressing AtTCTP. Interestingly, AtTCTP overexpression enhanced drought tolerance in plants. The expression analysis showed that AtTCTP was expressed in guard cells as well as in actively growing tissues. Physiological studies of the overexpression lines showed increased ABA- and calcium-induced stomatal closure ratios and faster stomatal closing responses to ABA. Furthermore, in vitro protein-protein interaction analysis confirmed the interaction between AtTCTP and microtubules, and microtubule cosedimentation assays revealed that the microtubule binding of AtTCTP increased after calcium treatment. These results demonstrate that the overexpression of AtTCTP confers drought tolerance to plants by rapid ABA-mediated stomatal closure via the interaction with microtubules in which calcium binding enhances the interaction. Collectively, the present results suggest that the plant TCTP has molecular properties similar to animal TCTPs, such as tubulin- and calcium-binding, and that it functions in ABA-mediated stomatal movement, in addition to regulating the growth of plants.