1,721,035 research outputs found
Effects of phytochelatin synthase on the secondary metabolism of Arabidopsis thaliana plants
No full textPhytochelatin synthase (PCS, EC 2.3.2.15) is a constitutively expressed cytosolic enzyme, found in a number of prokaryotes and eukaryotes, and amongst plants, preliminarily characterized in charophytes as well as in basal land plants (Degola et al., 2014; Petraglia et al., 2014).
At first, PCS was found to be involved in metal detoxification mechanisms (Grill et al., 1989). Nonetheless, the fact that PCS is ubiquitously expressed in the plant clade and in many other organisms, even in the complete absence of toxic metal(loid)s, would lead us to postulate other possible function(s) other than mere metal(loid) detoxification. In fact, PCS appears to be also involved in the catabolism of glutathione-conjugates (Beck et al., 2003), in camalexin production (Su et al., 2011) and in callose formation (Clay et al., 2009).
To better understand the functional roles of the enzyme besides metal detoxification, our work was aimed first at delineating Arabidopsis thaliana (At) metabolomics, in control and in Cd-exposed plants (shoots and roots). At this purpose, all metabolites from At wild-type (wt), PCS1 knockout mutant (cad1-3) and PCS-overexpressing mutant (AtPCS1-OE) were compared.
First of all, a different accumulation of glutathione (GSH), the substrate of PCS, was detected amongst the three plant lines. Indeed, the evidence of a higher GSH content found in cad1-3 mutants and a minor GSH content in AtPCS1-OE plants, suggests an important role of PCS to maintain GSH homeostasis. Furthermore, an accumulation of 4-methoxy-indol-3-ylmethylglucosinolate was detected in cad1-3 plants grown in the absence/presence of Cd. This glucosinolate is involved in callose production (Clay et al., 2009) and thus could contribute to defense mechanisms against pathogen attacks. Callose staining and pathogen assay experiments in our mutants showed that PCS protects plants against metal toxicity and also contributes to callose deposition; moreover, the PCS expression is essential to the resistance mechanism raised against the bacterium Pseudomonas syringae DC3000.
In addition, varying contents of flavonols were found among the three plant lines. An increase of kaempferol was measured in shoots and quercetin in roots of cad1-3 mutants, whilst lower amounts were found in AtPCS1-OE plants, compared with wt. Kaempferol and quercetin play several functions in the plant cell, among which the regulation of auxin efflux. Consequently, the content of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), indole-3-carboxylic acid (ICA) and indole-3-acetic acid methyl ester (MeIAA) was altered in mutant plants.
Not least, different levels of lignin precursors were found among the three plant lines exposed or not to Cd. As expected, stretch experiments proved a difference in terms of force/pressure required for breaking stems of the three plant lines, even grown in control conditions. Therefore, this work has highlighted for the first time potential new roles of AtPCS on cell wall remodeling, metabolism of phenilpropanoids, as well as modulation of auxin in planta distribution
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Bioprospecting the Italian Flora for The Discovery of New Bioactive Phytochemicals and the Exploration of Chemodiversity in Different Plant Clades
No full textWith more than 11,000 taxa of vascular and non-vascular plants and a high level of endemism, the Italian flora is among the richest and most diverse in Europe. Spanning over 400 plant families, this remarkable biodiversity is reflected into a wide variety of plant specialized metabolomes, which constitute a largely unexplored molecular reservoir with a significant potential for bioprospecting. Furthermore, this diverse chemical landscape represents a valuable framework to investigate the chemo-evolutive dynamics in land plants, research still limited by the structural and biosynthetic complexity of plant metabolites.
In the frame of the National Biodiversity Future Center, we launched a large-scale bioprospecting plan aimed at exploring the phytochemical diversity of the Italian flora with two main purposes: the discovery of novel bioactive compounds/phytocomplexes for human health and sustainable agriculture, and the comparison of plant metabolomes within specific evolutive clades to gain more information on the diversification of plant metabolism.
Over a three-year sampling campaign, we collected more than 700 species – about 75% native and 25% alien – from botanic gardens, nurseries and open-field. This collection is a simplified model of the Italian flora, in which, at least for higher plants, we included all Italian plant families according to their real relative amplitudes (e.g., for the Angiosperms, in order: Asteraceae, Poaceae, Fabaceae, Rosaceae, etc.). The untargeted metabolomics analysis through UPLC-HRMS guides the selection of the species with the most interesting phytochemical profiles towards a downstream bioactivity screening program focused on non-communicable diseases (e.g. neurodegenerative diseases, cancer, metabolic syndrome, etc.) and crop enhancement and protection. Currently, we have profiled about 300 species and some of them have already shown, for instance, promising results against colorectal cancer (Gratiola officinalis) and glioblastoma (Succisa pratensis), and anti-genotoxic activities (Cistus monspeliensis). In parallel to the phytochemical profiling, we are generating data for the relative comparison of the plant metabolomes from species belonging to the following clades: Asterids, Rosids, Monocots, Magnoliids, Gymnosperms, Lycophytes and Monylophytes, Bryophytes. Preliminary results for the Rosid clade (about 160 species in the collection) are shown
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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