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281.
Osmotin-expressing transgenic tea plants have improved stress tolerance and are of higher quality 总被引:1,自引:0,他引:1
Amita Bhattacharya Uksha Saini Robin Joshi Devinder Kaur Awadhesh Kumar Pal Nitish Kumar Ashu Gulati Prashant Mohanpuria Sudesh Kumar Yadav Sanjay Kumar Paramvir Singh Ahuja 《Transgenic research》2014,23(2):211-223
Drought is a major stress that affects the yield and quality of tea, a widely consumed beverage crop grown in more than 20 countries of the world. Therefore, osmotin gene-expressing transgenic tea plants produced using earlier optimized conditions were evaluated for their tolerance of drought stress and their quality. Improved tolerance of polyethylene glycol-induced water stress and faster recovery from stress were evident in transgenic lines compared with the normal phenotype. Significant improvements in growth under in-vitro conditions were also observed. Besides enhanced reactive oxygen species-scavenging enzyme activity, the transgenic lines contained significantly higher levels of flavan-3-ols and caffeine, key compounds that govern quality and commercial yield of the beverage. The selected transgenic lines have the potential to meet the demands of the tea industry for stress-tolerant plants with higher yield and quality. These traits of the transgenic lines can be effectively maintained for generations because tea is commercially cultivated through vegetative propagation only. 相似文献
282.
283.
Genomic imprinting in mammals: an interplay between chromatin and DNA methylation? 总被引:17,自引:0,他引:17
Most imprinted loci have key regulatory elements that are methylated on only one of the parental chromosomes. For several of these 'differentially methylated regions', recent studies establish that the unmethylated chromosome has a specialized chromatin organization that is characterized by nuclease hypersensitivity. The novel data raise the question of whether specific proteins and associated chromatin features regulate the allele-specificity of DNA methylation at these imprinting control elements. 相似文献
284.
Macrolide antibiotics such as erythromycin are clinically important polyketide natural products. We have engineered a recombinant strain of Escherichia coli that produces small but measurable quantities of the bioactive macrolide 6-deoxyerythromycin D. Bioassay-guided evolution of this strain led to the identification of an antibiotic-overproducing mutation in the mycarose biosynthesis and transfer pathway that was detectable via a colony-based screening assay. This high-throughput assay was then used to evolve second-generation mutants capable of enhanced precursor-directed biosynthesis of macrolide antibiotics. The availability of a screen for macrolide biosynthesis in E. coli offers a fundamentally new approach in dissecting modular megasynthase mechanisms as well as engineering antibiotics with novel pharmacological properties. 相似文献
285.
P. Rahi P. Vyas S. Sharma Ashu Gulati Arvind Gulati 《Indian journal of microbiology》2009,49(2):128-133
The ITS region sequence of a phosphate-solubilizing fungus isolated from the rhizosphere of tea growing in Kangra valley of
Himachal Pradesh showed 96% identity with Discosia sp. strain HKUCC 6626 ITS 1, 5.8S rRNA gene and ITS 2 complete sequence, and 28S rRNA gene partial sequence. The fungus exhibited
the multiple plant growth promoting attributes of solubilization of inorganic phosphate substrates, production of phytase
and siderophores, and biosynthesis of indole acetic acid (IAA)-like auxins. The fungal inoculum significantly increased the
root length, shoot length and dry matter in the test plants of maize, pea and chickpea over the uninoculated control under
the controlled environment. The plant growth promoting attributes have not been previously studied for the fungus. The fungal
strain with its multiple plant growth promoting activities appears attractive towards the development of microbial inoculants. 相似文献
286.
287.
Effects of gonadal and adrenal androgens in a novel androgen-responsive human osteoblastic cell line
Lorenz C. Hofbauer Kevin C. Hicok Sundeep Khosla 《Journal of cellular biochemistry》1998,71(1):96-108
While androgens have important skeletal effects, the mechanism(s) of androgen action on bone remain unclear. Current osteoblast models to study androgen effects have several limitations, including the presence of heterogeneous cell populations. In this study, we examined the effects of androgens on the proliferation and differentiation of a novel human fetal osteoblastic cell line (hFOB/AR-6) that expresses a mature osteoblast phenotype and a physiological number (∼4,000/nucleus) of androgen receptors (AR). Treatment with 5α-dihydrotestosterone (5α-DHT) inhibited the proliferation of hFOB/AR-6 cells in a dose-dependent fashion, while it had no effect on the proliferation of hFOB cells, which express low levels of AR (<200/nucleus). In hFOB/AR-6 cells, co-treatment with the specific AR antagonist, hydroxyflutamide abolished 5α-DHT-induced growth inhibition. Steady-state levels of transforming growth factor-β1 (TGF-β1) and TGF-β-induced early gene (TIEG) mRNA decreased after treatment of hFOB/AR-6 cells with 5α-DHT, suggesting a role for the TGF-β1-TIEG pathway in mediating 5α-DHT-induced growth inhibition of hFOB/AR-6 cells. In support of this, co-treatment of hFOB/AR-6 cells with TGF-β1 (40 pg/ml) reversed the 5α-DHT-induced growth inhibition, whereas TGF-β1 alone at this dose had no effect on hFOB/AR-6 cell proliferation. Furthermore, treatment of hFOB/AR-6 cells with 5α-DHT and testosterone (10−8 M) inhibited basal and 1,25-(OH)2D3-induced alkaline phosphatase (ALP) activity and type I collagen synthesis without affecting osteocalcin production. Thus, in this fetal osteoblast cell line expressing a physiological number of AR, androgens decrease proliferation and the expression of markers associated with osteoblast differentiation. These studies suggest that the potential anabolic effect of androgens on bone may not be mediated at the level of the mature osteoblast. J. Cell. Biochem. 71:96–108, 1998. © 1998 Wiley-Liss, Inc. 相似文献
288.
Overexpression of an activated rasG gene during growth blocks the initiation of Dictyostelium development. 下载免费PDF全文
Transformants that expressed either the wild-type rasG gene, an activated rasG-G12T gene, or a dominant negative rasG-S17N gene, all under the control of the folate-repressible discoidin (dis1gamma) promoter, were isolated. All three transformants expressed high levels of Ras protein which were reduced by growth in the presence of folate. All three transformants grew slowly, and the reduction in growth rate correlated with the amount of RasG protein produced, suggesting that RasG is important in regulating cell growth. The pVEII-rasG transformant containing the wild-type rasG gene developed normally despite the presence of high levels of RasG throughout development. This result indicates that the down regulation of rasG that normally occurs during aggregation of wild-type strains is not essential for the differentiation process. Dictyostelium transformants expressing the dominant negative rasG-S17N gene also differentiated normally. Dictyostelium transformants that overexpressed the activated rasG-G12T gene did not aggregate. The defect occurred very early in development, since the expression of car1 and pde, genes that are normally induced soon after the initiation of development, was repressed. However, when the transformant cells were pulsed with cyclic AMP, expression of both genes returned to wild-type levels. The transformants exhibited chemotaxis to cyclic AMP, and development was synergized by mixing with wild-type cells. Furthermore, cells that were pulsed with cyclic AMP for 4 h before being induced to differentiate by plating on filters produced small, but otherwise normal, fruiting bodies. These results suggest that the rasG-G12T transformants are defective in cyclic AMP production and that RasG - GTP blocks development by interfering with the initial generation of cyclic AMP pulses. 相似文献
289.
Crystal structure of an Acyl-ACP dehydrogenase from the FK520 polyketide biosynthetic pathway: insights into extender unit biosynthesis 总被引:4,自引:0,他引:4
Polyketide synthases (PKSs) synthesize the polyketide cores of pharmacologically important natural products such as the immunosuppressants FK520 and FK506. Understanding polyketide biosynthesis at atomic resolution could present new opportunities for chemo-enzymatic synthesis of complex molecules. The crystal structure of FkbI, an enzyme involved in the biosynthesis of the methoxymalonyl extender unit of FK520, was solved to 2.1A with an R(crys) of 24.4%. FkbI has a similar fold to acyl-CoA dehydrogenases. Notwithstanding this similarity, the surface and substrate-binding site of FkbI reveal key differences from other acyl-CoA dehydrogenases, suggesting that FkbI may recognize an acyl-ACP substrate rather than an acyl-CoA substrate. This structural observation coincided the genetic experiment done by Carroll et al. J. Am. Chem. Soc., 124 (2002) 4176. Although an in vitro assay for FkbI remains elusive, the structural basis for the substrate specificity of FkbI is analyzed by a combination of sequence comparison, docking simulations and structural analysis. A biochemical mechanism for the role of FkbI in the biosynthesis of methoxymalonyl-ACP is proposed. 相似文献
290.