Finding new ways to fight plant diseases.
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Plant breeders have used disease resistance genes (R genes) to control plant disease since the turn of the century. Molecular cloning of R genes that enable plants to resist a diverse range of pathogens has revealed that the proteins encoded by these genes have several features in common. These findings suggest that plants may have evolved common signal transduction mechanisms for the expression of resistance to a wide range of unrelated pathogens. Characterization of the molecular signals involved in pathogen recognition and of the molecular events that specify the expression of resistance may lead to novel strategies for plant disease control.
The content of major carcinogenic and genotoxic polyaromatic hydrocarbons (PAH) in urban air, vehicle, and industrial emissions is assessed. A sensitive, specific, and selective method for PAH and nitro-PAH quantitation was developed on the basis of low-temperature luminescence-spectra of frozen polycrystalline solutions. Polyarene contents in urban air and urban industrial emissions, as well as vehicle exhausts, are compared to the Russian Ministry of Health standard of maximal permissible concentration for benzo[a]pyrene in the ambient air. Special attention was paid to the study of PAH profiles and characteristics of different sources. The feasibility of using benzo[a]pyrene to assess PAH content in industrial and vehicle emissions was explored. PAH profiles in the ambient air and local emissions are compared. In addition, genotoxicity of the emissions of coke plant and diesel engine exhausts are compared to their polyarene content.
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In recent years, actions have been undertaken by the Belgian government to promote process innovation and technical diversification. Research programs are initiated and coordinated by the study committee for biotechnology setup within the Institute for Scientific Research in Industry and Agriculture (IRSIA). As a result of this action, the main areas where biotechnological processes are developed or commercially exploited include plant genetics, protein engineering, hybridoma technology, biopesticides, production by genetic engineering of vaccines and drugs, monoclonal detection of human and animal deseases, process reactors for aerobic and anaerobic wastewater treatment, and genetic modification of yeast and bacteria as a base for biomass and energy. Development research also includes new fermentation technologies principally based on immobilization of microorganisms, reactor design, and optimization of unit operations involved in downstream processing. Food, pharmaceutical, and chemical industries are involved in genetic engineering and biotechnology and each of these sectors is overviewed in this paper.
Artemisinin, a new and a very potent antimalarial drug, is produced by the Chinese medicinal herb Artemisia annua L. It is a sesquiterpene lactone with an endoperoxide bridge and is active against chloroquine resistant forms of Plasmodium falciparum. The relatively low yield (0.01% - 0.6%) of artemisinin in A. annua is a serious limitation to the commercialization of the drug. Therefore, a through understanding of the biosynthetic pathway and the characterization of the involved enzymes are important for the biology production of artemisinin. This review is focused on the recent progress in the molecular regulation of artemisinin biosynthesis from the following aspects: the biosynthetic pathway of artemisinin, the key enzymes involved in artemisinin biosynthesis, and the molecular regulation of artemisinin biosynthesis. The biosynthetic pathway of artemisinin belongs to the isoprenoid metabolite pathway, the key enzymes involved in the biosynthesis of artemisinin include: 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), farnesyl diphosphate synthase (FDPS), and amorpha-4, 11-diene synthase, of which amorpha-4, 11-diene synthase catalyzes the cyclisation of the ubiquitous precursor farnesyl diphosphate to the highly specific olefinic sesquiter-pene skeletons and has been postulated as the regulatory step in the biosynthesis of artemisinin. Recently the gene encoding of the amorpha-4, 11-diene synthase has been cloned and the functional expressions have been studied by several research teams, therefore, the breakthroughs in production of artemisinin could hopefully be achieved by metabolic engineering of the plant, in particular, by over-expressing enzyme(s) catalyzing the rate limiting step(s) of artemisinin biosynthesis or by inhibiting the enzyme(s) of other pathway competing for its precursors. Besides, the effects of the heterogenesis isoprenoid pathway related genes on artemisinin biosynthesis of the transformed plants were also discussed.
While ServiceMaster is a service organization like many health care providers and provider-sponsored shared services, its range of services, hospitals served and geographic distribution of services make it the largest shared service in the nation. ServiceMaster manages laundry and houskeeping, and supplies plant and biomedical engineering and materiel management services to more than 800 hospitals throughout the United States. Some of these services are high-technology oriented. All require excellence in products, methods and people skills.
Various strategies have been developed to exploit plants as bioreactors for the production of pharmaceutical antibodies, to engineer antibody-mediated pathogen resistance or to alter the plant phenotype by immunomodulation. Recent research developments focus on the fine-tuning of expression systems and the detailed characterisation of recombinant products, including the implications of plant-specific glycosylation. Meanwhile, the first of these plant-derived antibody products has successfully completed early phase clinical trials.
The use of plants and bacterial to clean up environmental pollutants has gained momentum in past years. A limitation to phytoremediation of solvents has been toxicity of the compounds to plants, and the uncertainty as to the fate of many of the compounds. In a recent study, engineered endophytes have been shown to increase plant tolerance to toluene, and to decrease the transpiration of toluene to the atmosphere. This type of work has the potential to increase the use of phytoremediation by decreasing toxicity and increasing degradation of toxins.
The genetic basis of multiple phenotypic alterations was studied in cell-engineered cybrids Nicotiana tabacum (+ Hyoscyamus niger) combining the nuclear genome of N. tabacum, plastome of H. niger and recombinant mitochondria. The plants possess a complex, maternally inheritable syndrome of nucleo-cytoplasmic incompatibility, severely affecting growth, metabolism and development. In vivo, the syndrome was manifested as: late germination of seeds; dramatic decrease of chlorophyll and carotenoids in cotyledons and leaves; altered morphology of cotyledons, leaves and flowers; and dwarfism. The leaf phenotype depended on light intensity. In 'green flowers' (an extreme phenotype), homeotic function B was downregulated. In vitro, the incompatibility syndrome was restricted to the pigment deficiency of cotyledons. Electron microscopy revealed perturbations in the differentiation of chloroplasts and palisade parenchyma cells in bleached leaves. The pigment deficiency accompanied by retarded growth is discussed as a result of plastome-genome incompatibility, whereas other features are likely to be due to nucleo-mitochondrial incompatibilities.
Current knowledge of the etiology of prostate cancer is limited. Numerous studies have suggested that certain occupations and industries may be associated with the occurrence of prostate cancer. Information on occupation and industry on death certificates from 24 states gathered from 1984 to 1993 was used in case control study on prostate cancer. A total of 60,878 men with prostate cancer as underlying cause of death was selected and matched with controls who died of all other causes except cancer. Similar to the findings of our parallel large case control study of prostate cancer, we observed excess risks in some white-collar occupations, such as administrators, managers, teachers, engineers, and sales occupations. However, some blue-collar occupations, such as power plant operators and stationary engineers, brickmasons, machinery maintenance workers, airplane pilots, longshoreman, railroad industry workers, and other occupations with potential exposure to PAH also showed risk of excess prostate cancer. Risk was significantly decreased for blue-collar occupations, including farm workers, commercial fishermen, mechanics and repairers, structural metal workers, mining, printing, winding, dry cleaning, textile machine operators, cooks, bakers, and bartenders. Although we observed excess risks of prostate cancer among some low socioeconomic status (SES) occupations, the overall results suggest that the effects of higher SES cannot be ruled out in associations between occupational factors and the risk of prostate cancer.
Tomato yellow leaf curl disease (TYLCD) is caused by a group of geminiviruses that belong to the Tomato yellow leaf curl virus (TYLCV) complex and are transmitted by the whitefly (Bemisia tabaci Genn.). The disease causes great yield losses in many countries throughout the Mediterranean region and the Middle East. In this study, the efficacy of post-transcriptional gene silencing (PTGS) to control the disease caused by TYLCV complex was investigated. Non-coding conserved regions from the genome of TYLCV, Tomato yellow leaf curl virus-mild, tomato yellow leaf curl Sardinia virus, tomato yellow leaf curl Malaga virus, and tomato yellow leaf curl Sardinia virus-Spain [2] were selected and used to design a construct that can trigger broad resistance against different viruses that cause tomato yellow leaf curl disease. The silencing construct was cloned into an Agrobacterium-binary vector in sense and antisense orientation and used in transient assay to infiltrate tomato and Nicotiana benthamiana plants. A high level of resistance was obtained when plants were agro-infiltrated with an infectious clone of the Egyptian isolate of TYLCV (TYLCV-[EG]) or challenge inoculated with TYLCV, TYLCV-Mld, and TYLCSV-ES[2] using whitefly-mediated transmission 16-20 days post infiltration with the silencing construct. Results of the polymerase chain reaction showed that the resistance was effective against all three viruses. Furthermore, dot blot hybridization and PCR failed to detect viral DNA in symptomless, silenced plants. A positive correlation between resistance and the accumulation of TYLCV-specific siRNAs was observed in silenced plants. Together, these data provide compelling evidence that PTGS can be used to engineer geminivirus-resistant plants.
Plants are constantly exposed to a large array of pathogenic organisms and the survival in these conditions demands quick defense responses which include the synthesis of defense peptides and proteins with antimicrobial properties. The main groups of antimicrobial peptides found in plants are thionins, defensins and lipid transfer proteins. They constitute interesting candidates to engineer disease resistance in plants.
Chitinases are functional in plant defense against pathogens and also involved in plant development as well as human disease responses. In this study a chitinase gene, Wch2, from wheat was expressed transiently in tobacco leaves and stably in transgenic Arabidopsis thaliana plants to evaluate its heterologous expression and potential application. Western blot analysis revealed that the expressed wheat chitinase was about 30 kD as was expected (Fig.1) and had hydrolytic activity towards chitin polymers (Fig.2). Integration and expression of Wch2 gene in transgenic Arabidopsis were confirmed by PCR (Fig.3) and Western blot (Fig.4) analyses. Wch2 accumulated to a high level in transgenic plants without any detectable degradation. Transgenic plants expressing Wch2 displayed a much higher resistance to Fusarium oxysporum f. sp. matthiolae, a fungus infectious to Arabidopsis thaliana than the plants containing green fluorescence protein (GFP) (Fig.5). These results indicated that Wch2 was suitable for heterologous expression in different organisms and could be used for enhancement of plant resistance in genetic engineering. The Arabidopsis-Fusarium interaction may be one of the ideal plant-fungus interaction systems for the evaluation of antifungal proteins in planta.
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The increased production of trienoic fatty acids, hexadecatrienoic (16:3) and linolenic (18:3) acids, is a response connected with cold acclimation of higher plants and is thought to protect plant cells against cold damage. Transgenic tobacco (Nicotiana tabacum cv SR1) plants that contain increased levels of 16:3 and 18:3 fatty acids, and correspondingly decreased levels of their precursors, hexadecadienoic and linoleic acids, were engineered by introduction of a chloroplast [omega]-3 fatty acid desaturase gene (the fad7 gene) isolated from Arabidopsis thaliana. When exposed to 1[deg]C for 7 d and then cultured at 25[deg]C, the suppression of leaf growth observed in the wild-type plants was significantly alleviated in the transgenic plants with the fad7 gene. The low-temperature- induced chlorosis was also much reduced in the plants transformed with the fad7 gene. These results indicate that increased levels of trienoic fatty acids in genetically engineered plants enhance cold tolerance.
Cold storage of potato (Solanum tuberosum L.) tubers is known to cause accumulation of reducing sugars. Hexose accumulation has been shown to be cultivar-dependent and proposed to be the result of sucrose hydrolysis via invertase. To study whether hexose accumulation is indeed related to the amount of invertase activities, two different approaches were used: (i) neutral and acidic invertase activities as well as soluble sugars were measured in cold-stored tubers of 24 potato cultivars differing in the cold-induced accumulation of reducing sugars and (ii) antisense potato plants with reduced soluble acid invertase activities were created and the soluble sugar accumulation in cold-stored tubers was studied. The cold-induced hexose accumulation in tubers from the different potato cultivars varied strongly (up to eightfold). Large differences were also detected with respect to soluble acid (50-fold) and neutral (5-fold) invertase activities among the different cultivars. Although there was almost no correlation between the total amount of invertase activity and the accumulation of reducing sugars there was a striking correlation between the hexose/sucrose ratio and the extractable soluble invertase activity. To exclude the possibility that other cultivar-specific features could account for the obtained results, the antisense approach was used to decrease the amount of soluble acid invertase activity in a uniform genetic background. To this end the cDNA of a cold-inducible soluble acid invertase (EMBL nucleic-acid database accession no. X70368) was cloned from the cultivar Desirée, and transgenic potato plants were created expressing this cDNA in the antisense orientation under control of the constitutive 35S cauliflower mosaic virus promotor. Analysis of the harvested and cold-stored tubers showed that inhibition of the soluble acid invertase activity leads to a decreased hexose and an increased sucrose content compared with controls. As was already found for the different potato cultivars the hexose/sucrose ratio decreased with decreasing invertase activities but the total amount of soluble sugars did not significantly change. From these data we conclude that invertases do not control the total amount of soluble sugars in cold-stored potato tubers but are involved in the regulation of the ratio of hexose to sucrose.