1,720,957 research outputs found
Studies on the intron-dependent meristematic expression of the dihydrofolate reductase/thymidylate synthase (DRTS) genes of Arabidopsis thaliana
No full textIn plants, dihydrofolate reductase (DHFR) and thymidylate synthase (TS) constitute a bifunctional enzyme (DRTS) which is essential for the synthesis of DNA precursors in proliferating or endoreduplicating cells. Previous characterizations of the three AtDRTS genes of Arabidopsis thaliana revealed distinctive patterns of expression and a crucial positive control of AtDRTS1 expression in apical meristems by an intragenic region containing the second intron of the gene [1]. In this study we report that the strong meristematic expression of AtDRTS2 is also strictly dependent on the first intron located in the 5’UTR of the gene. However, sequence comparisons of the first intron of AtDRTS2 and the second intron of AtDRTS1 could not detect common regions and a serial mutation analysis of the first AtDRTS2 intron could not identify regulatory elements enabling the meristematic activity of the gene. Nevertheless, the 5’UTR of AtDRTS2 is capable to confer strong meristematic expression when placed downstream of the AtDRS1 promoter suggesting an interchangeability between the two different introns and lack of specificity between promoter and intronic sequences. In addition, we found that the 5’UTR of AtDRTS2 acts at the transcriptional level and can confer meristematic activity also to the promoter of the AtBAM3 gene of A. thaliana, which is strongly and specifically expressed only in leaf tissues. This meristematic activating capacity, however, is not observed with a minimal 35S promoter which indicates that the first intron of AtDRTS2 cannot act autonomously as a promoter by itself but must interplay with additional regulatory regions
Studies on the regulatory regions of a DHFR/TS gene of Arabidopsis thaliana controlling its expression in root meristems.
No full textUsing a synthetic plant promoter to assess E2F-dependent transcriptional activation in Arabidopsis thaliana
No full textSynthetic promoters specifically targeted by a single family of transcription factors (TFs) can reveal important clues on TFs roles and regulation. In this study, a synthetic promoter construct has been used to analyse the transcriptional activation by E2F factors in Arabidopsis thaliana. The typical E2F factors are key components of the cyclin D/retinoblastoma/E2F pathway which controls cell proliferation and other cellular processes in both plants and animals [1]. The typical E2Fs activate gene expression binding DNA together with Dimerisation Partner (DP) proteins but can acquire repressive roles by interacting with retinoblastoma-related (RBR) proteins. Moreover, atypical E2Fs that lack transactivating ability and act independently of DPs and RBR increase the complexity of E2F-mediated transcriptional regulation [2]. To analyse E2F-dependent activation in planta we transformed Arabidopsis thaliana with a GUS reporter construct controlled by a synthetic promoter (EM35S) composed of 10 repetitions of a canonical E2F binding site (TTTCGCGC) placed upstream to a minimal –60 CaMV 35S promoter. Analyses of the transformed lines revealed a cell cycle-dependent activation of the reporter gene in the G1/S phase in proliferating cells but disclosed a differential expression in the meristems of shoots versus roots which is likely linked to the contrasting action of activating and repressing E2Fs. Moreover, the constitutive over-expression of an exogenous typical E2F factor from carrot [1] is capable to overcome the endogenous control of the synthetic promoter and an assessment of the regulatory circuits controlling the typical E2Fs of Arabidopsis thaliana suggests a regulation of the activating E2Fs through direct phosphorylation
Functional analysis of TDP-43, the main cause of familiar Amyotrophic Lateral Sclerosis in Sardinia
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
GFP-based reporters to monitor biochemical alteration in cellular models for Amyotrophic Lateral Sclerosis
No full textVariations 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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