1,720,976 research outputs found
THE FEMALE GAMETOPHYTE: DEVELOPMENT AND FUNCTION
Full text linkThe plant life cycle alternates the diploid sporophyte and the haploid gametophyte. The female gametophyte of flowering plants develops within the ovule, a specialized structure within the ovary, which gives rise to the seed after fertilization.
Sexual reproduction in plants entails a series of developmental steps that culminate in the formation of the seed. The developing ovule protects the haploid female gametophyte, which is formed as the result of the megasporogenesis and megagametogenesis. Inside the female gametophyte, the two female gametic cells, the central and the egg cells, upon fertilization give rise to the seed endosperm and embryo respectively.
During my PhD, I dissect the genetic and molecular networks controlling female gametophyte formation and differentiation. I employed a yeast one-hybrid approach to identify EC1.1 regulators; the EC1 genes are specifically expressed in the female gamete and they are required for gamete fusion, therefore they are good candidates for clarify how gamete differentiation occurs in Arabidopsis thaliana. Among the transcription factors isolated, we focused on SUPPRESSOR OF FRIGIDA4 (SUF4). In vivo and in vitro evidences support SUF4 capacity to regulate AtEC1.1, furthermore suf4 mutants show also a mild ec1 phenotype.
Plant can produce progeny without sexual reproduction. One example is apomixis, where meiosis and fertilization of the egg by male gametes are by passed to result in the production of clonal progeny without a parental contribution. Apomixis is due to modifications of the sexual reproduction and it does not occur in the major crop species, but is found in many wild species like Poa pratensis and Brachiaria brizantha.
The idea of this work is to study genes involved in apomixis in apomictic plants, and then studies the function in the model organism Arabidopsis thaliana.
In Poa pratensis by the cDNA-AFLP technique several genes differentially expressed in apomictic and sexual genotypes have been isolated.
During my PhD I characterized the Arabidopsis homologue of PpAPO1 (Poa pratensis APOSTART 1) that has been renamed AtAPO1.
Brachiaria brizantha is an important forage grass. The occurrence of both apomictic and sexual reproduction within Brachiaria makes it an interesting system for understanding the molecular pathways involved in both modes of reproduction
AtAPOSTART1, an Arabidopsis thaliana PH-START domain protein involved in seed germination
No full textThe seed in the mature and dry state is metabolically inactive (quiescent) and is thus able to withstand extreme environmental conditions, such as drought and cold. Germination commences when the dry seed, shed from its parent plant, takes up water (imbibition) and ends when the root emerges through the seed coat. During seedling establishment, the reserves stored in the seed are metabolized, whereas the subsequent vegetative and reproductive growth is supported by photosynthesis. Here, we describe the functional characterization of the PH-START protein AtAPO1 (Arabidopsis thaliana APOSTART1), the putative homologue of PpAPO1 (Poa pratensis APOSTART1) in Arabidopsis thaliana. By using translational fusion of the AtAPO1 promoter to the uiaD gene and in situ hybridization analyses, we show that AtAPO1 is expressed in mature embryo sacs and developing embryos. The functional analysis of two at-apostart mutant alleles suggests that AtAPO1 is involved in the control of seed germination
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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