1,720,967 research outputs found
Isozyme diversity, RFLP of the rDNA and phylogenetic affinities among cultivated Lima beans, Phaseolus lunatus (Fabaceae). Plant. Systematics and Evolution.
No full textLectin and lectin-related proteins in lima bean (Phaseolus lunatus L.) seeds: biochemical and evolutionary studies
No full textLectin-related polypeptides are a class of defence proteins found in seeds of Phaseolus species. In Lima bean (P. lunatus), these proteins and their genes have been well characterized in the Andean morphotype, which represents one of the two gene pools of this species. To study the molecular evolution of the lectin family in Lima bean we characterized the polypeptides belonging to this multigene family and cloned the genes belonging to the Mesoamerican gene pool. The latter gene pool contains components similar to those of the Andean pool, namely: an amylase inhibitor-like (AIL), an arcelin-like (ARL) lectin and the less abundant Lima bean lectin (LBL). These proteins originate from an ancestor gene of the lectin type which duplicated to yield the lectin gene and the progenitor of ARL and AIL. In this species, ARL represents an evolutionary intermediate form that precedes AIL. Phylogenetic analysis supports an Andean origin for Lima bean. The molecular evolutionary studies were extended to the genes of common bean and demonstrated that true lectin genes and the ancestor of lectin-related genes are the result of a duplication event that occurred before speciation. Lima and common bean followed different evolutionary pathways and in the latter species a second duplication event occurred that gave rise, in Mesoamerican wild genotypes, to arcelin genes
Genotyping-by-sequencing reveals molecular genetic diversity in Italian common bean landraces
Full text linkThe common bean (Phaseolus vulgaris L.) is one of the main legumes worldwide and represents a valuable source of nutrients. Independent domestication events in the Americas led to the formation of two cultivated genepools, namely Mesoamerican and Andean, to which European material has been brought back. In this study, Italian common bean landraces were analyzed for their genetic diversity and structure, using single nucleotide polymorphism (SNP) markers derived from genotyping-by-sequencing (GBS) technology. After filtering, 11,866 SNPs were obtained and 798 markers, pruned for linkage disequilibrium, were used for structure analysis. The most probable number of subpopulations (K) was two, consistent with the presence of the two genepools, identified through the phaseolin diagnostic marker. Some landraces were admixed, suggesting probable hybridization events between Mesoamerican and Andean material. When increasing the number of possible Ks, the Andean germplasm appeared to be structured in two or three subgroups. The subdivision within the Andean material was also observed in a principal coordinate analysis (PCoA) plot and a dendrogram based on genetic distances. The Mesoamerican landraces showed a higher level of genetic diversity compared to the Andean landraces. Calculation of the fixation index (FST) at individual SNPs between the Mesoamerican and Andean genepools and within the Andean genepool evidenced clusters of highly divergent loci in specific chromosomal regions. This work may help to preserve landraces of the common bean from genetic erosion, and could represent a starting point for the identification of interesting traits that determine plant adaptation
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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