1,721,197 research outputs found
Contribution à l’étude des mécanismes moléculaires de l’hyperaccumulation de métaux chez Arabidopsis halleri
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Interaction croisée de l’homéostasie du fer et du zinc chez Arabidopsis : Contribution du gène FRD3
No full textGoing 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
Functional characterization of Arabidopsis HMA4 P-type ATPases
No full textTransition metals play a vital role in the development and survival of photosynthetic organisms. Therefore, plants require a metal homeostasis network to control their inner metal concentration despite variation in metal supply. The HMA4 membrane protein has a central role in the zinc homeostasis network of the model plant Arabidopsis thaliana. This PIB-2 ATPase loads zinc (and cadmium) from the pericycle cells into the xylem in roots. It is involved in zinc hyperaccumulation as well as zinc and cadmium hypertolerance in the pseudometallophyte Arabidopsis halleri. In particular, the enhanced expression of HMA4 in A. halleri compared to A. thaliana triggers a higher translocation of metal from root to shoot.
As a PIB ATPase, the HMA4 architecture consists of a transmembrane domain, two cytoplasmic catalytic domains, the actuator domain and the ATP-binding domain divided in a nucleotide-binding domain and a phosphorylation domain, as well as N- and C-terminal cytosolic extensions. Thanks to high conservation level within the P-type ATPases, the role of the HMA4 cytoplasmic catalytic domains can be inferred from well characterized pumps of the family. In contrast, the function of its terminal cytosolic extensions as well as the metal permeation mechanism through the membrane remains elusive.
A combined in vivo and in vitro functional characterization pointed out the importance of high affinity Zn2+ binding to the HMA4 N- terminal extension C27CxxE31 motif and the C-terminal extension di-Cys motifs for the function of the protein in plants. This study also suggested the presence in the C-terminal extension of a signal for the HMA4 localization in the plasma membrane. Finally, the high divergence of coding sequence between the A. thaliana and A. halleri HMA4 C-terminal extensions does not result in major functional differences between the two proteins, at least when expressed in A. thaliana.
Moreover, a structural analysis by homology modeling of the HMA4 transmembrane region highlighted amino acids forming a metal permeation pathway, whose importance was subsequently investigated functionally through mutagenesis and complementation experiments in plants. The analysis newly identified amino acids whose mutation results in total or partial loss of the protein function. In addition, the comparison of zinc and cadmium accumulation in shoots of A. thaliana complemented lines revealed a number of HMA4 mutants exhibiting different abilities in zinc and cadmium translocation.
Altogether this work significantly advanced our understanding of the function of HMA4, a key protein of the zinc homeostasis network in plants
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
Molecular basis of zin homeostasis in Arabidopsis and Brachypodium model plants
No full textZinc (Zn) is an essential micronutrient for all life forms. Zn has a cofactor role in all classes of enzymes and is involved in multiple molecular, cellular and physiological functions. Plants, and crops in particular, also need enough amount of this transition metal for their growth and for yield produc-tion. They are additionally an important source of Zn for animals and humans and around two billion people are depending on legumes and grains as their main Zn source. Zn is however toxic for plants at high concentrations. The eudicot Arabidopsis thaliana (Arabidopsis) and monocot rice model spe-cies have been widely used for physiological and molecular studies of Zn homeostasis under various Zn regimes. These studies have resulted in the identification and characterization of multiple gene families of Zn transporters, the most important of which is ZRT, IRT-like Protein (ZIP) family. How-ever, the sophisticated signaling and regulation mechanisms behind Zn uptake, transport and translo-cation in plants remain unclear. Aiming at revealing these mechanisms, our group has dissected the dynamic response to changes in Zn depletion and resupply. First, time-resolved sampling strategy in Arabidopsis allowed concomitant quantification of the dynamics of Zn uptake, microsomal and solu-ble proteins, and specific transcripts, in space (root and shoot) and time. Zn-responding signaling/reg-ulatory molecules included receptor and MAP kinases, calcium signaling proteins, phosphoinositides, G-proteins, COP9 signalosome members, as well as multiple transcription factors. We selected a list of candidate proteins and upon phenotyping the mutant lines, further characterized three final candi-dates. This part of the work was however unsuccessful to identify a clear link between candidate pro-teins and Zn homeostasis in Arabidopsis. Second, we aimed at investigating Zn homeostasis in mon-ocot model plant Brachypodium distachyon (Brachypodium). Although some important players of Zn uptake and transport have been studied in wheat, barley and especially rice, it is unclear how different or similar are the responses of monocots and eudicots to Zn supply at the molecular level. Rice, on the other hand, is not an ideal and perfect model of Zn/iron studies for all monocots. We studied the physiological, ionome and transcriptome response of Brachypodium to static and dynamic Zn supply. Our studies showed that Brachypodium responds to Zn deficiency and excess in all the mentioned levels and has a high potential to be extensively used as a model plant in Zn studies for monocots especially for wheat and barley. Moreover, we showed that ZIP family genes are strongly regulated in shoot upon Zn resupply before any Zn was translocated to shoot, which is indicative of root-to-shoot signaling. Collectively, we showed that studying rapid molecular response of plants to Zn resupply after deficiency reveals new aspects of the Zn homeostasis network. We also introduce Brachypodium as a new and efficient model for Zn studies
Insights into zinc homeostasis mechanisms in the Root Apical Meristem of two Arabidopsis species.
No full textDispelling 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
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