1,720,958 research outputs found
Pattern di espressione del gene Ppi1 e analisi di mutanti ppi1 e ppi 2 in Arabidopsis thaliana
No full textThe proton pump interactor (Ppi) gene family of Arabidopsis thaliana: expression pattern of Ppi1 and characterisation of knockout mutants for Ppi1 and 2. Plant plasma membrane H+-ATPases (PM H+-ATPase) are essential for establishing a proton electrochemical gradient across the cell plasma membrane. Their regulation is poorly understood, except for the role of 14-3-3 proteins, which relieve autoinhibition from the C-terminal domain. A novel protein interacting with this domain was recently identified in Arabidopsis and named PPI1 (Proton Pump Interactor 1). PPI1 stimulates PM H+-ATPase activity in vitro. Here, we analyse the expression pattern of Ppi1 using b-glucuronidase as a reporter. Expression is strong in root and shoot vascular systems, particularly in meristematic and sink tissues, as well as in pollen, stigmas and siliques, but not in developing embryos. Removal of the first intron decreased GUS expression 45-fold. We also analysed the transcription of Ppi2, another gene in the family, and demonstrated that Ppi2 is expressed in seedlings, cultured cells and flowers. Insertional mutants for both Ppi1 and Ppi2 were isolated. Two different mutants of Ppi1 showed aberrant mRNAs and lacked any detectable protein and are therefore true knockouts. At the plant level, neither of the single mutants nor the double ppi1ppi2 mutant showed an altered phenotype in standard growth conditions under acid load or salt stress
Analyzing Ppi1 gene expression using promoter-GUS fusions
No full textPPI1 (PROTON PUMP INTERACTOR 1) is a protein identified in a two hybrid screen whose Nterminus binds to the Arabidopsis thaliana plasma membrane proton pump (PM H+-ATPase). The entire PPI1 protein, or fragments thereof, expressed as fusion protein in E. coli, are able to stimulate the activity of the proton pump in vitro (Morandini et al., 2002 Plant J. 31:487-97).
To study the pattern of Ppi1 expression we produced transgenic reporter lines with the GUS gene under the control of Ppi1 promoter. Since the gene presents a large intron before the beginning of the coding region (a so-called ‘leader intron’), we decided to test three different constructs. The first contains both the promoter and the leader intron; the second one is lacking the leader intron but still contains the Ppi1 5’UTR; the last one is missing the intron and the 5’UTR derives from the TMV.
In an alternative approach to study the function of the PPI1 protein we make use of Arabidopsis KO lines bearing a T-DNA insertion. Two lines were characterized in detail for Ppi1: an insertion in intron I (line N93) and one in exon VII (line F09) at aa 525. These KO lines were confirmed with RT-PCR and western analysis. The Ppi1 KO lines do not show evident phenotype when grown in pots. In contrast, KO culture cells seems to grow faster, to release a brown compound and to form tracheary elements at higher frequencies than the WT
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
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