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Regulatie van het vitamine C metabolisme in vruchten
No full textL-Ascorbic acid (AsA), or vitamin C, is an abundant low molecular dietary antioxidant compound that exerts a protective role against chronic diseases and disorders in humans. Genetic control of AsA concentrations in fruits can involve biosynthetic, recycling and transport mechanisms, as well as being linked to changes in whole fruit metabolism and/or plant growth. The aim of this work was to understand the genetics underlying the control of vitamin C metabolism in fruits. Two major approaches have been employed using two different fruit crops tomato and apple. Both species have medium AsA levels, but the significant variation among different cultivars (particularly in apple) clearly indicates that there is potential for improvement of this trait. In the first phase of this work, extensive biochemical analyses, as well as 14C-labelled and non-labelled substrate feeding experiments were carried out in various tissues and fruit ripening stages in two tomato cultivars. Results confirm that the L-galactose pathway is the main AsA biosynthetic route in tomato fruits, but substrates from alternative pathways can also be converted to AsA in fruits at specific developmental stages and genotypes. Overall, both biosynthetic capacity and the turnover rate of the AsA pool decline throughout ripening. However, the two tomato cultivars (AsA-rich Santorini and AsA-poor Ailsa Craig) exhibited different profiles of AsA accumulation during ripening, but a characteristic peak in AsA-totAsA concentrations at the breaker stage. Differences in the activity of AsA recycling enzymes (particularly of MDHAR) helped explain the variations in fruit AsA concentrations of the two cultivars. In addition, expression profiles of an orthologue of GDP-L-galactose phosphorylase (SlGGP1), and two gene copies of monodehydroascorbate reductase (SlMDHAR1 and SlMDHAR3) were all closely associated with changes in AsA concentrations throughout ripening. Among these candidate genes, the expression of SlGGP1 was closely related with high AsA concentrations at red ripe fruits. To investigate the role of ethylene, two mutants inhibited in their ethylene responses (Never-ripe and ripening-inhibitor) were also studied. Results clearly indicate a key role of ethylene receptors in the control of fruit AsA pool that should be further investigated. In parallel with the tomato work, a combination of molecular, genetic and genomic approaches (QTL mapping, NGS, SNP discovery, gene expression and allelic association studies) were used to help identify key genes regulating fruit AsA concentrations in apple tissues. Stable AsA-QTLs over two or three years of measurements were mapped in LGs 10, 11, and 17. Candidate gene mapping demonstrated that the three paralogues of MdGGP are key regulators of AsA and totAsA concentrations in mature apple. Further, allelic variations in the transcript sequences of MdGGP1 (LG 11) and MdGGP3 (LG 10) arecloselylinked to fruit totAsA concentrations both within the Telamon x Braeburn mapping population and across a selection of commercial cultivars. Results from gene expression studies (qPCR) confirm that the expression of MdGGP1 and MdGGP3, as well as of a paralogue of dehydroascorbate reductase (MdDHAR3-3), are all strongly associated with fruit AsA concentrations in a selection of high- and low-vitamin C cultivars. These SNP-based markers are thus potentially excellent candidate for use within breeding programs to screen for progeny with increased AsA concentrations. At last, MdDHAR3 was found to have a key role in regulating the redox state of the AsA pool in apple fruits, and increased flesh DHA concentrations are associated with susceptibility to flesh browning. The separation of fruit into green and red side is beneficial for the better understanding of fruit AsA regulation, as highlighted by the improvement of AsA-QTL size and properties. The combined results in tomato and apple allow us to suggest that GGP has a central role in regulating fruit AsA levels which is broadly applicable at different fruit species. In terms of applied research, the identification of novel genes/alleles linked to high fruit AsA concentrations in apple can have immediate applications within fruit breeding programs via marker assisted breeding and screening.<w:latentstyles < <w:latentstyles="" semihidden="false" priority="0" locked="false" status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Considerations to prevent the breakdown and loss of fruit carotenoids during extraction and analysis in Musa
Get PDFThe impact of treatments aimed at improving the robustness of protocols for the analysis of carotenoids in fruit of banana and plantain were examined. Neither the inclusion of polyvinylpolypyrrolidine in the extraction buffer, nor vigorous homogenisation with glass beads influenced recoveries or chromatographic profiles. By contrast, heating lead to losses of up to 53% and to the formation of degradation products that are no longer detectable on our RP-HPLC system. Carotenoid extracts are unstable and most sensitive to exposure to light. However, even in the dark at -20 degrees C and in the presence of antioxidants breakdown rates of around 5% per day were observed.sponsorship: The authors thank Otto van Poeselaere and Eva A. Davey for help in the preparation of the manuscript and Peter Salaets for technical help. The authors acknowledge financial support from CGIAR-Bioversity and the Harvest Plus Global Challenge program on Nutritional Enhancement and Biodiversity, as well as Inge van den-Berg from Bioversity International, Montpellier, France and Gerard Bertin Ngoh-Newilah of CARBAP, Cameroon. (CGIAR-Bioversity, Harvest Plus Global Challenge, Inge van den-Berg from Bioversity International, Montpellier, France, Gerard Bertin Ngoh-Newilah of CARBAP, Cameroon)status: Publishe
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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