1,720,961 research outputs found
Molecular investigation of RAD51 and DMC1 homoeologous genes of hexaploid wheat (Triticum aetivum L.)
No full textMeiotic recombination in eukaryotes requires two orthologues of the E. coli RecA proteins, Rad51 and Dmc1. Both genes play an important role in the binding of single strand DNA, homology search, strand invasion and strand exchange resulting in Holliday junctions which are resolved into crossovers or non-crossovers events. Even though both genes are well characterized in a variety of organisms including plants, very little information is available from hexaploid wheat. In most diploid plant species, deletion of either the RAD51 or DMC1 orthologues leads to sterility but wheat being a polyploid, offers a unique opportunity to examine the effects of the deletion of specific homoeologue, while maintaining a degree of fertility. The transcript expression profiling of RAD51 and DMC1 genes in Arabidopsis, rice and wheat using available microarray databases indicated higher levels of expression in mitotically and meiotically active tissues compared to other tissues. However, the possible function of the DMC1 gene in mitotic-active tissues needs to be investigated further. Previously cDNA sequences of TaRAD51 and TaDMCl of hexaploid wheat were cloned and reported. In this study, it has been demonstrated that the reported TaRAD51A1 and TaRAD51A2 cDNA sequences are (D) and (A) homoeologues of TaRAD51 respectively and TaDMCl cDNA sequence is (D) homoeologue of the TaDMC1. This study also found that the amino acid sequences and evolutionary relationships of RAD51 and DMC1 cDNA homoeologues are highly conserved across eukaryotes. Functional characterization of TaRAD51 and TaDMCl gene homoeologues was undertaken in planta using Forward Genetics, Reverse Genetics and Complementation methods. Forward and Reverse Genetic screening of a subset of a Highbury mutant population could not identify any mutants that have deletions in TaRAD51 and TaDMC1 genes. However, Reverse Genetics screening of Paragon mutant population identified mutant lines that tested as having deletions for all the three homoeologues of TaRAD51 and TaDMCl. However, most likely due to high mutational load and a deleterious phenotype, only a few mutant lines survived. Phenotypic and cytogenetic analysis indicated the probable functional redundancy of TaRAD51 (B) homoeologue in meiosis, although the unknown size of the deletion and limited phenotype makes it impossible to completely certain of this. The single mutants for TaDMC1 (B) and (D) indicated a reduction in pollen viability and ear fertility compared to wild-type. The cytological examination of these mutants indicated low levels of abnormal diakinesis, resulting in the formation of dyads. However, the single mutants were still able to produce normal tetrads. This suggests that there is a possible dosage effect of these homoeologues in hexaploid wheat. Unless deletion lines for the (A) and (D) homoeologues of TaRAD51 and (B) homoeologue of TaDMC1 can be recovered and characterized the above assumptions will remain inconclusive. The results of complementation assays using over-expressing CaMV35S::TaRAD51(D)±GFP constructs demonstrated a very low (-14% and -2%, respectively, with +GFP and -OFP constructs) functional complementation in terms of seed set compared to 0% in homozygous Atrad51 mutants. One explanation of these results is that the wheat genes are not complete functional orthologues for the inactivated Arabidopsis genes. The functional complementation experiments could not be performed for TaDMC1 gene because of time limitation, although the transformants were produced in AtDMC1/atdmc1 background. Finally, overexpression of the TaRAD51 gene suggests 2-fold increase in genetic distances in Arabidopsis using CaMV35S::TaRAD51(D) construct. This was done by crossing the appropriate transformant with fluorescent tetrad lines. However the results need to be confirmed by a large scale analysis
Molecular investigation of RAD51 and DMC1 homoeologous genes of hexaploid wheat (Triticum aetivum L.)
Full text linkMeiotic recombination in eukaryotes requires two orthologues of the E. coli RecA proteins, Rad51 and Dmc1. Both genes play an important role in the binding of single strand DNA, homology search, strand invasion and strand exchange resulting in Holliday junctions which are resolved into crossovers or non-crossovers events. Even though both genes are well characterized in a variety of organisms including plants, very little information is available from hexaploid wheat. In most diploid plant species, deletion of either the RAD51 or DMC1 orthologues leads to sterility but wheat being a polyploid, offers a unique opportunity to examine the effects of the deletion of specific homoeologue, while maintaining a degree of fertility. The transcript expression profiling of RAD51 and DMC1 genes in Arabidopsis, rice and wheat using available microarray databases indicated higher levels of expression in mitotically and meiotically active tissues compared to other tissues. However, the possible function of the DMC1 gene in mitotic-active tissues needs to be investigated further. Previously cDNA sequences of TaRAD51 and TaDMCl of hexaploid wheat were cloned and reported. In this study, it has been demonstrated that the reported TaRAD51A1 and TaRAD51A2 cDNA sequences are (D) and (A) homoeologues of TaRAD51 respectively and TaDMCl cDNA sequence is (D) homoeologue of the TaDMC1. This study also found that the amino acid sequences and evolutionary relationships of RAD51 and DMC1 cDNA homoeologues are highly conserved across eukaryotes. Functional characterization of TaRAD51 and TaDMCl gene homoeologues was undertaken in planta using Forward Genetics, Reverse Genetics and Complementation methods. Forward and Reverse Genetic screening of a subset of a Highbury mutant population could not identify any mutants that have deletions in TaRAD51 and TaDMC1 genes. However, Reverse Genetics screening of Paragon mutant population identified mutant lines that tested as having deletions for all the three homoeologues of TaRAD51 and TaDMCl. However, most likely due to high mutational load and a deleterious phenotype, only a few mutant lines survived. Phenotypic and cytogenetic analysis indicated the probable functional redundancy of TaRAD51 (B) homoeologue in meiosis, although the unknown size of the deletion and limited phenotype makes it impossible to completely certain of this. The single mutants for TaDMC1 (B) and (D) indicated a reduction in pollen viability and ear fertility compared to wild-type. The cytological examination of these mutants indicated low levels of abnormal diakinesis, resulting in the formation of dyads. However, the single mutants were still able to produce normal tetrads. This suggests that there is a possible dosage effect of these homoeologues in hexaploid wheat. Unless deletion lines for the (A) and (D) homoeologues of TaRAD51 and (B) homoeologue of TaDMC1 can be recovered and characterized the above assumptions will remain inconclusive. The results of complementation assays using over-expressing CaMV35S::TaRAD51(D)±GFP constructs demonstrated a very low (-14% and -2%, respectively, with +GFP and -OFP constructs) functional complementation in terms of seed set compared to 0% in homozygous Atrad51 mutants. One explanation of these results is that the wheat genes are not complete functional orthologues for the inactivated Arabidopsis genes. The functional complementation experiments could not be performed for TaDMC1 gene because of time limitation, although the transformants were produced in AtDMC1/atdmc1 background. Finally, overexpression of the TaRAD51 gene suggests 2-fold increase in genetic distances in Arabidopsis using CaMV35S::TaRAD51(D) construct. This was done by crossing the appropriate transformant with fluorescent tetrad lines. However the results need to be confirmed by a large scale analysis.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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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