1,720,956 research outputs found
Inducibility, tissue-specificity and product variation of three phytochelatin synthase homeologs from the cadmiumtolerant reed A. donax L.
No full textPhytochelatins (PC) are a family of Cys-rich oligopeptides constituting the main defence of plants against toxicity of heavy
metals and metalloids like cadmium and arsenic. PCs are non-ribosomally synthesized from glutathione by the enzyme
phytochelatin synthase (PCS). Dicotyledonous PCS have been characterized in detail, while much less information is
available on monocotyledonous ones. In this study, we characterized three different PCS genes from giant reed (Arundo
donax L.), a biomass/bionergy crop with remarkable tolerance to cadmium, to study the evolution of this trait in monocots.
Phylogenetic reconstruction with PCS genes from fully sequenced monocotyledonous genomes indicated that the three A.
donax PCS, AdPCS1-3, are most likely homeologs - resulting from lineage-specific whole-genome polyploidization.
AdPCS1-3 genes are tissue-specifically expressed, and AdPCS1 is expressed about 5 times more than AdPCS2 and
AdPCS3. All three genes displayed cadmium-responsive expression in roots, and coded for functional PCSs, as once
overexpressed in yeast they confer enhanced tolerance to cadmium stress. Overexpression of AdPCS1-3 in Arabidopsis
thaliana further confirmed the typical phenoytype associated to overexpression of functional PCS genes. Mass-spectral
analyses detected statistically significant differences in the amount and spectral feature of the PCs synthesized, with
AdPCS2 and AdPCS1 producing, respectively, the highest and lowest amount of total PCs in yeast cells. AdPCS1
synthesized the same amount of PC2, PC3 and PC4, while both AdPCS2 and AdPCS3 enzymes produced significantly
higher amounts of PC2 and PC3 compared to PC4.
Taken together, these results indicate that the genetic bases of A. donax high capability to tolerate the presence of heavy
metals is, at least in part, related to the high functional specialization of its PCS genes from a transcriptional as well as
enzymatic point of view. Thus, transcriptional neofunctionalization and specialization seems to have played a major role in
the evolution of Cd tolerance in A. donax
Evolution and functional differentiation of recently diverged phytochelatin synthase genes from Arundo donax L.
Full text linkPhytochelatin synthases (PCSs) play pivotal roles in the detoxification of heavy metals and metalloids in plants; however, little information on the evolution of recently duplicated PCS genes in plant species is available. Here we characterize the evolution and functional differentiation of three PCS genes from the giant reed (Arundo donax L.), a biomass/bioenergy crop with remarkable resistance to cadmium and other heavy metals. Phylogenetic reconstruction with PCS genes from fully sequenced monocotyledonous genomes indicated that the three A. donax PCSs, namely AdPCS1-3, form a monophyletic clade. The AdPCS1-3 genes were expressed at low levels in many A. donax organs and displayed different levels of cadmium-responsive expression in roots. Overexpression of AdPCS1-3 in Arabidopsis thaliana and yeast reproduced the phenotype of functional PCS genes. Mass spectrometry analyses confirmed that AdPCS1-3 are all functional enzymes, but with significant differences in the amount of the phytochelatins synthesized. Moreover, heterogeneous evolutionary rates characterized the AdPCS1-3 genes, indicative of relaxed natural selection. These results highlight the elevated functional differentiation of A. donax PCS genes from both a transcriptional and an enzymatic point of view, providing evidence of the high evolvability of PCS genes and of plant responsiveness to heavy metal stress
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
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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