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Search Results: 1 - 10 of 167753 matches for " E. Lundgren "
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Trichome-Specific Expression of Amorpha-4,11-Diene Synthase, a Key Enzyme of Artemisinin Biosynthesis in Artemisia annua L., as Reported by a Promoter-GUS Fusion  [PDF]
Hongzhen Wang, Linda Olofsson, Anneli Lundgren, Peter E. Brodelius
American Journal of Plant Sciences (AJPS) , 2011, DOI: 10.4236/ajps.2011.24073
Abstract: Artemisia annua L. produces small amounts of the sesquiterpenoid artemisinin, which is used for treatment of malaria. A worldwide shortage of the drug has led to intense research to increase the yield of artemisinin in the plant. In order to study the regulation of expression of a key enzyme of artemisinin biosynthesis, the promoter region of the key enzyme amorpha-4,11-diene synthase (ADS) was cloned and fused with the β-glucuronidase (GUS) reporter gene. Transgenic plants of A. annua expressing this fusion were generated and studied. Transgenic plants expressing the GUS gene were used to establish the activity of the cloned promoter by a GUS activity staining procedure. GUS under the control of the ADS promoter showed specific expression in glandular trichomes. The activity of the ADS promoter varies temporally and in old tissues essentially no GUS staining could be observed. The expression pattern of GUS and ADS in aerial parts of the transgenic plant was essentially the same indicating that the cis-elements controlling glandular trichome specific expression are included in the cloned promoter. However, some cis-element(s) that control expression in root and old leaf appears to be missing in the cloned promoter. Furthermore, qPCR was used to compare the activity of the wild-type ADS promoter with that of the cloned ADS promoter. The latter promoter showed a considerably lower activity than the wild-type promoter as judged from the levels of GUS and ADS transcripts, respectively, which may be due to the removal of an enhancing cis-element from the ADS promoter. The ADS gene is specifically expressed in stalk and secretory cells of glandular trichomes of A. annua.
Relative expression of genes of terpene metabolism in different tissues of Artemisia annua L
Linda Olofsson, Alexander Engstr?m, Anneli Lundgren, Peter E Brodelius
BMC Plant Biology , 2011, DOI: 10.1186/1471-2229-11-45
Abstract: The four genes of the artemisinin biosynthetic pathway (amorpha-4,11-diene synthase, amorphadiene-12-hydroxylase, artemisinic aldehyde ?11(13) reductase and aldehyde dehydrogenase 1) showed remarkably higher expression (between ~40- to ~500-fold) in flower buds and young leaves compared to other tissues (old leaves, stems, roots, hairy root cultures). Further, dihydroartemisinic aldehyde reductase showed a very high expression only in hairy root cultures. Germacrene A and caryophyllene synthase were mostly expressed in young leaves and flower buds while epi-cedrol synthase was highly expressed in old leaves. 3-Hydroxy-3-methyl-glutaryl coenzyme A reductase exhibited lower expression in old leaves compared to other tissues. Farnesyldiphosphate synthase, squalene synthase, and 1-deoxy-D-xylulose-5-phosphate reductoisomerase showed only modest variation in expression in the different tissues, while expression of 1-deoxy-D-xylulose-5-phosphate synthase was 7-8-fold higher in flower buds and young leaves compared to old leaves.Four genes of artemisinin biosynthesis were highly expressed in flower buds and young leaves (tissues showing a high density of glandular trichomes). The expression of dihydroartemisinic aldehyde reductase has been suggested to have a negative effect on artemisinin production through reduction of dihydroartemisinic aldehyde to dihydroartemisinic alcohol. However, our results show that this enzyme is expressed only at low levels in tissues producing artemisinin and consequently its effect on artemisinin production may be limited. Finally, squalene synthase but not other sesquiterpene synthases appears to be a significant competitor for farnesyl diphosphate in artemisinin-producing tissues.The genus Artemisia, belonging to the Asteraceae family, contains a large number of aromatic plants. During the latest decades, A. annua L. (annual or sweet wormwood) has received increasing attention due to the fact that the plant produces the sesquiterpenoid endo
Informed consent - where do we stand in South Africa in 2004?: comment
Christina Lundgren
Southern African Journal of Anaesthesia and Analgesia , 2004,
Live From Moscow: The Celebration Of Yuri Gagarin And Transnational Television In Europe
Lars Lundgren
View : Journal of European Television History and Culture , 2012,
Abstract: On April 14th, 1961, television viewers across Europe watched live images of Yuri Gagarin being celebrated on the Red Square in Moscow. The broadcast was made possible by the linking of the Intervision and Eurovision television networks, which was the result of cooperation between broadcasters on both sides of the Iron Curtain. By looking into how the co-operation between the OIRT and EBU was gradually developed between 1957 and 1961 this article engages with the interplay between cultural, legal and technological aspects of broadcasting and how the transnational broadcast of Gagarin’s return to Moscow was made possible. The article furthermore argues the need to understand early television in Europe as a dialectic between the national and the transnational and shows how the live transmission network binding the East and West together was the result of an interplay between structures provided by transnational organisations such as the OIRT and EBU, and initiatives by national broadcasting organisations.
When to start: not so fast
Lundgren J
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18071
Abstract: It remains controversial whether and, if so, the extent to which antiretroviral therapy (ART) results in net benefit if used by HIV-positive persons with a high CD4 count, particularly those with early HIV infection. This controversy is primarily reflecting lack of solid evidence from randomized controlled trials. Currently published trials have compared early ART with initiation of ART below currently globally accepted thresholds for initiation (i.e. CD4 count at 350 cells/μL) and, hence, are unable to inform this discussion. Analyses on large observational studies that have attempted to address this question have shown inconsistent results; therefore, those results are considered low-quality evidence, as per the GRADE criteria used by, for example, WHO when formulating guidelines. In resource-constrained regions, not even observational data are available to inform this question. The START study is underway to answer this question. Data remain blinded, but START may show net harm from early use of ART; such a result would severely undermine use of ART as prevention in early HIV infection. Prescription of any type of medicine is guided by the principle of “do no harm” – that is, “the doctor should not prescribe medications unless s/he knows that the treatment is unlikely to be harmful.” Hence, the balance of risk/benefit to individuals versus prevention benefit is important to accurately determine, and current guidelines of generally initiating ART once the patient develops HIV-related symptoms or the CD4 count drops to levels around 350 cells/μL should be adhered to until further evidence has emerged.
Momentum-Space Entanglement in Heisenberg Spin-Half Ladders
Rex Lundgren
Physics , 2014,
Abstract: We analytically study momentum-space entanglement in quantum spin-half ladders consisting of two coupled critical XXZ spin-half chains using field theoretical methods. When the system is gapped, the momentum-space entanglement Hamiltonian is described by a conformal field theory with a central charge of two. This is in contrast to entanglement Hamiltonians of various real-space partitions of gapped-spin ladders that have a central charge of one. When the system is gapless, we interestingly find that the entanglement Hamiltonian consist of one gapless mode linear in subsystem momentum and one mode with a flat dispersion relation. We also find that the momentum-space entanglement entropy obeys a volume law.
Bt Crop Effects on Functional Guilds of Non-Target Arthropods: A Meta-Analysis
L. LaReesa Wolfenbarger, Steven E. Naranjo, Jonathan G. Lundgren, Royce J. Bitzer, Lidia S. Watrud
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002118
Abstract: Background Uncertainty persists over the environmental effects of genetically-engineered crops that produce the insecticidal Cry proteins of Bacillus thuringiensis (Bt). We performed meta-analyses on a modified public database to synthesize current knowledge about the effects of Bt cotton, maize and potato on the abundance and interactions of arthropod non-target functional guilds. Methodology/Principal Findings We compared the abundance of predators, parasitoids, omnivores, detritivores and herbivores under scenarios in which neither, only the non-Bt crops, or both Bt and non-Bt crops received insecticide treatments. Predators were less abundant in Bt cotton compared to unsprayed non-Bt controls. As expected, fewer specialist parasitoids of the target pest occurred in Bt maize fields compared to unsprayed non-Bt controls, but no significant reduction was detected for other parasitoids. Numbers of predators and herbivores were higher in Bt crops compared to sprayed non-Bt controls, and type of insecticide influenced the magnitude of the difference. Omnivores and detritivores were more abundant in insecticide-treated controls and for the latter guild this was associated with reductions of their predators in sprayed non-Bt maize. No differences in abundance were found when both Bt and non-Bt crops were sprayed. Predator-to-prey ratios were unchanged by either Bt crops or the use of insecticides; ratios were higher in Bt maize relative to the sprayed non-Bt control. Conclusions/Significance Overall, we find no uniform effects of Bt cotton, maize and potato on the functional guilds of non-target arthropods. Use of and type of insecticides influenced the magnitude and direction of effects; insecticde effects were much larger than those of Bt crops. These meta-analyses underscore the importance of using controls not only to isolate the effects of a Bt crop per se but also to reflect the replacement of existing agricultural practices. Results will provide researchers with information to design more robust experiments and will inform the decisions of diverse stakeholders regarding the safety of transgenic insecticidal crops.
Transient Expression of Hemagglutinin Antigen from Low Pathogenic Avian Influenza A (H7N7) in Nicotiana benthamiana
Selvaraju Kanagarajan, Conny Tolf, Anneli Lundgren, Jonas Waldenstr?m, Peter E. Brodelius
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033010
Abstract: The influenza A virus is of global concern for the poultry industry, especially the H5 and H7 subtypes as they have the potential to become highly pathogenic for poultry. In this study, the hemagglutinin (HA) of a low pathogenic avian influenza virus of the H7N7 subtype isolated from a Swedish mallard Anas platyrhynchos was sequenced, characterized and transiently expressed in Nicotiana benthamiana. Recently, plant expression systems have gained interest as an alternative for the production of vaccine antigens. To examine the possibility of expressing the HA protein in N. benthamiana, a cDNA fragment encoding the HA gene was synthesized de novo, modified with a Kozak sequence, a PR1a signal peptide, a C-terminal hexahistidine (6×His) tag, and an endoplasmic retention signal (SEKDEL). The construct was cloned into a Cowpea mosaic virus (CPMV)-based vector (pEAQ-HT) and the resulting pEAQ-HT-HA plasmid, along with a vector (pJL3:p19) containing the viral gene-silencing suppressor p19 from Tomato bushy stunt virus, was agro-infiltrated into N. benthamiana. The highest gene expression of recombinant plant-produced, uncleaved HA (rHA0), as measured by quantitative real-time PCR was detected at 6 days post infiltration (dpi). Guided by the gene expression profile, rHA0 protein was extracted at 6 dpi and subsequently purified utilizing the 6×His tag and immobilized metal ion adsorption chromatography. The yield was 0.2 g purified protein per kg fresh weight of leaves. Further molecular characterizations showed that the purified rHA0 protein was N-glycosylated and its identity confirmed by liquid chromatography-tandem mass spectrometry. In addition, the purified rHA0 exhibited hemagglutination and hemagglutination inhibition activity indicating that the rHA0 shares structural and functional properties with native HA protein of H7 influenza virus. Our results indicate that rHA0 maintained its native antigenicity and specificity, providing a good source of vaccine antigen to induce immune response in poultry species.
Studies on the Expression of Sesquiterpene Synthases Using Promoter-β-Glucuronidase Fusions in Transgenic Artemisia annua L
Hongzhen Wang, Junli Han, Selvaraju Kanagarajan, Anneli Lundgren, Peter E. Brodelius
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080643
Abstract: In order to better understand the influence of sesquiterpene synthases on artemisinin yield in Artemisia annua, the expression of some sesquiterpene synthases has been studied using transgenic plants expressing promoter-GUS fusions. The cloned promoter sequences were 923, 1182 and 1510 bp for β-caryophyllene (CPS), epi-cedrol (ECS) and β-farnesene (FS) synthase, respectively. Prediction of cis-acting regulatory elements showed that the promoters are involved in complex regulation of expression. Transgenic A. annua plants carrying promoter-GUS fusions were studied to elucidate the expression pattern of the three sesquiterpene synthases and compared to the previously studied promoter of amorpha-4,11-diene synthase (ADS), a key enzyme of artemisinin biosynthesis. The CPS and ECS promoters were active in T-shaped trichomes of leaves and stems, basal bracts of flower buds and also in some florets cells but not in glandular secretory trichome while FS promoter activity was only observed in leaf cells and trichomes of transgenic shoots. ADS, CPS, ECS and FS transcripts were induced by wounding in a time depended manner. The four sesquiterpene synthases may be involved in responsiveness of A. annua to herbivory. Methyl jasmonate treatment triggered activation of the promoters of all four sesquiterpene synthases in a time depended manner. Southern blot result showed that the GUS gene was inserted into genomic DNA of transgenic lines as a single copy or two copies. The relative amounts of CPS and ECS as well as germacrene A synthase (GAS) transcripts are much lower than that of ADS transcript. Consequently, down-regulation of the expression of the CPS, ECS or GAS gene may not improve artemsinin yield. However, blocking the expression of FS may have effects on artemisinin production.
Evidence for the Active Phase of Heterogeneous Catalysts through In Situ Reaction Product Imaging and Multiscale Modeling
S. Matera,S. Blomberg,M. J. Hoffmann,J. Zetterberg,J. Gustafson,E. Lundgren,K. Reuter
Physics , 2015,
Abstract: We use multi-scale modeling to analyze laser-induced fluorescence (LIF) measurements of the CO oxidation reaction over Pd(100) at near-ambient reaction conditions. Integrating density-functional theory based kinetic Monte Carlo simulations of the active catalyst into fluid-dynamical simulations of the mass transport inside the reactor chamber we calculate the reaction product concentration directly above the catalyst surface. Comparing corresponding data calculated for different surface models against the measured LIF signals we can discriminate the one that predominantly actuates the experimentally measured catalytic activity. For the probed CO oxidation reaction conditions the experimental activity is due to pristine Pd(100), possibly coexisting with other (oxidic) domains on the surface.
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