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1.
Four mutants that show the delayed leaf senescence phenotype were isolated from Arabidopsis thaliana . Genetic analyses revealed that they are all monogenic recessive mutations and fall into three complementation groups, identifying three genetic loci controlling leaf senescence in Arabidopsis . Mutations in these loci cause delay in all senescence parameters examined, including chlorophyll content, photochemical efficiency of photosystem II, relative amount of the large subunit of Rubisco, and RNase and peroxidase activity. Delay of the senescence symptoms was observed during both age-dependent in planta senescence and dark-induced artificial senescence in all of the mutant plants. The results indicate that the three genes defined by the mutations are key genetic elements controlling functional leaf senescence and provide decisive genetic evidence that leaf senescence is a genetically programmed phenomenon controlled by several monogenic loci in Arabidopsis . The results further suggest that the three genes function at a common step of age-dependent and dark-induced senescence processes. It is further shown that one of the mutations is allelic to ein2-1 , an ethylene-insensitive mutation, confirming the role of ethylene signal transduction pathway in leaf senescence of Arabidopsis .  相似文献   
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Bacterial lipoproteins play an important role in bacterial pathogenesis and physiology. The genome of Campylobacter jejuni, a major foodborn pathogen, is predicted to contain over 20 lipoproteins. However, the functions of the majority of C. jejuni lipoproteins remain unknown. The Cj0090 protein is encoded by a lipoprotein operon composed of cj0089, cj0090, and cj0091. Here, we report the crystal structure of Cj0090 at 1.9 Å resolution, revealing a novel variant of the immunoglobulin fold with β‐sandwich architecture. The structure suggests that Cj0090 may be involved in protein‐protein interactions, consistent with a possible role for bacterial lipoproteins. Proteins 2012;. © 2012 Wiley Periodicals, Inc.  相似文献   
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The effect of initial sucrose concentration was investigated in root suspension cultures of Morinda citrifolia to improve root growth and secondary metabolites production, i.e. anthraquinone, phenolics and flavonoids. Besides, oxidative stress level, antioxidant enzymes activity and membranes damage under different sucrose concentration were estimated. A 5% sucrose supply was shown to be optimal for the production of root dry mass, but higher sucrose concentrations of 7–9% inhibited the accumulation of root dry weight (DW). However, the maximum production of anthraquinone (251.89 g L−1 DW), phenolics (165.14 g L−1 DW) and flavonoids (163.56 g L−1 DW) were achieved at 1% sucrose-treated culture, which may be a source carbon skeletons for secondary metabolism. At the same time was observed low oxidative damage, which could be associated with high levels of secondary metabolites and the increased activity of catalase. Although, catalase (CAT) activity were stimulated at 7–9% sucrose-treated cultures, high accumulation of hydrogen peroxide (H2O2) and peroxidation of lipid (MDA) was induced. The observed high activity of CAT and guaiacol peroxidase (G-POD) were not sufficient enough to mitigate the toxic effect of H2O2.  相似文献   
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The effects of aluminum on lipid peroxidation and activities of antioxidative enzymes were investigated in detached rice leaves treated with 0 to 5 mM AlCl3 at pH 4.0 in the light. AlCl3 enhanced the content of malondialdehyde but not the content of H2O2. Superoxide dismutase activity was reduced by AlCl3, while catalase and glutathione reductase activities were increased. Peroxidase and ascorbate peroxidase activities were increased only after prolonged treatment, when toxicity occurred. The results give evidence that Al treatment caused oxidative stress and in turn, it caused lipid peroxidation.  相似文献   
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近年来,植物遗传转化研究有了长足的发展。已经达到能够通过简单的遗传控制手段研究具有新表现型的植物,甚至达到进入商业化的程度。这些手段包括植物生物学的主要研究技术以及植物组织培养和树种改良的一些实用方法。尽管采用农瘤杆菌和鸟枪法等技术的植物遗传转化系统已经得到了广泛的应用,但是在如何开发具有能够得到控制表达的转基因高产植物方面,在如何使所得到的转基因植物远离遗传危害等方面,目前的转化系统遇到了极大的技术挑战。已经提出了各种各样的方法用于将新基因稳定地导入120多种不同植物的核基因组。本文将讨论这些遗传转化系统所需的生物学要求和实际应用方面的需求、基因转化和转基因表达的研究策略、遗传转化植物的鉴定以及转基因植物与大众的认可。本文将分为七个部分加以讨论:一、导言;二 、基因转化到细胞里的方法;三、植物遗传转化策略;四、植物遗传转化的鉴定;五、植物遗传转化的实际应用;六、转基因植物与环境;七、未来植物遗传转化的需求与发展方向。  相似文献   
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Summary In vitro plantlets of Phalaenopsis ‘Happy Valentine’, Neofinetia falcate Hu, Cymbidium kanran Makino, and Cymbidium goeringii Reichb. f. were grown under photoautotrophic [high photosynthetic photon flux (PPF), high CO2 concentration, and increased number of air exchanges] and heterotrophic (low PPF, low CO2 concentration, no air exchanges) culture conditions. After 40 d of culture, a significant difference in plantlet growth was observed between the two cultures. Total fresh and dry mass were on average 1.5 times greater in photoautotrophic culture than in heterotrophic culture. Higher net photosynthetic rates were also observed for Phalaenopsis in photoautotrophic culture. In photoautotrophic culture, little difference was observed in air temperature between the inside and outside of the culture vessel, whereas in heterotrophic culture, air temperature inside the culture vessel was 1–2°C higher than that outside the culture vessel. Relative humidity inside the culture vessel was remarkably different between the two cultures: 83–85% in photoautotrophic culture and 97–99% in heterotrophic culture. These results indicated that growth and net photosynthetic rate of in vitro orchid plantlets were susceptible to the culture environments such as PPF, CO2 concentration, relative humidity (RH), and the number of air exchanges, which would allow a more efficient micropropagation system for these orchid plants.  相似文献   
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Harvestable, starch-storing organs of plants, such as fleshy taproots and tubers, are important agronomic products that are also suitable target organs for use in the molecular farming of recombinant proteins due to their strong sink strength. To exploit a promoter directing strong expression restricted to these storage organs, we isolated the promoter region (3.0 kb) of SRD1 from sweetpotato (Ipomoea batatas cv. ‘White Star’) and characterized its activity in transgenic Arabidopsis, carrot, and potato using the β-glucuronidase (GUS) gene (uidA) as a reporter gene. The SRD1 promoter conferred root-specific expression in transgenic Arabidopsis, with SRD1 promoter activity increasing in response to exogenous IAA. A time-course study of the effect of IAA (50 μM) revealed a maximum increase in SRD1 promoter activity at 24 h post-treatment initiation. A serial 5′ deletion analysis of the SRD1 promoter identified regions related to IAA-inducible expression as well as regions containing positive and negative elements, respectively, controlling the expression level. In transgenic carrot, the SRD1 promoter mediated strong taproot-specific expression, as evidenced by GUS staining being strong in almost the entire taproot, including secondary phloem, secondary xylem and vascular cambium. The activity of the SRD1 promoter gradually increased with increasing diameter of the taproot in the transgenic carrot and was 10.71-fold higher than that of the CaMV35S promoter. The SRD1 promoter also directed strong tuber-specific expression in transgenic potato. Taken together, these results demonstrate that the SRD1 promoter directs strong expression restricted to the underground storage organs, such as fleshy taproots and tubers, as well as fibrous root tissues.  相似文献   
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The present study reports an efficient protocol for indirect shoot organogenesis and plantlets regeneration of Withania somnifera (L.) Dunal. Leaf explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of 6-benzylaminopurine (BAP) and indole-3-acetic acid (IAA). The highest callus induction rate (89.5 %) and shoot regeneration rate (92 %) were obtained when 2 mg dm−3 BAP was combined with 0.5 mg dm−3 IAA. Three major withanolides (withaferine A, 12-deoxywithastramonolide and withanolide A) were investigated in different plant organs from in vitro and greenhouse grown plants. Leaves contained higher contents of withanolides and phenolics than roots or stems, whereas roots contained the highest contents of flavonoids and polysacharides. In vitro grown plants contained greater contents of phenolics, flavonoids and polysaccharides while lower contents of withanolides than greenhouse grown plants.  相似文献   
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