1,721,017 research outputs found
Two Endopolygalacturonase Genes in Trichoderma virens: In Silico Characterization and Expression during Interaction with Plants
No full textThe ability of Trichoderma spp. to antagonize most phytopathogenic fungi and to interact with plants by inducing their resistance and promoting their growth has been widely described. Endopolygalacturonases (endoPGs) produced by Trichoderma spp. can assist root penetration and play a pre-eliciting role in induced systemic resistance (ISR), a beneficial effect detected in plants colonized by Trichoderma. In this study, two endoPG genes (Tvpg1 and Tvpg2) have been identified and partially characterized in a T. virens isolate, previously investigated for its antagonistic ability in several biological systems. An extensive in silico analysis showed relatively low sequence similarities (53%) between TvPG1 and TvPG2 proteins and underscored interesting phylogenetic relationships in the comparison of endoPG genes among fungal genomes. The phylogeny of endoPGs suggests a differentiation in action mechanisms associated with biological functions as one cluster shows only genes from plant-interacting organisms. A gene expression analysis demonstrated a different regulation pattern for those genes. The Tvpg1 gene was induced both when the fungus was grown in liquid cultures supplemented with pectin or plant cell walls and when it was applied to tomato roots in a growth chamber. Expression times were comparable in both systems. On the contrary, the Tvpg2 gene displayed a constitutive expression in all conditions tested, including controls. The molecular communication between tomato roots and T. virens was investigated by checking the expression of a tomato PGIP (Lepgip1) in roots colonized by fungal mycelium. The Lepgip1 transcript was induced at times coincident with Tvpg1 expression, suggesting a correlation between the two gene products. This paper reports the results of first investigations of T. virens endoPG genes performed on a structural, phylogenetic and functional level
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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