1,720,961 research outputs found
Analysis of auxin fluxes carring to senescence of the embryonic root and the formation of crown roots in the species Setaria viridis
No full textSetaria viridis tem sido utilizada como organismo modelo para gramíneas com metabolismo C4, buscando elucidar processos biológicos de plantas. A importância das monocotiledôneas com o metabolismo de C4 deve-se ao melhor balanço fotossintético quando comparado às plantas com metabolismo C3 em condições climáticas com altas temperaturas, como as que prevalecem no Brasil. Setaria viridis representa um sistema modelo de grande importância para a agricultura brasileira, uma vez que tanto a produção brasileira de biocombustíveis como de alimentos está fortemente relacionada aos organismos C4. Os hormônios vegetais são cruciais no estabelecimento de órgãos complexos desde o zigoto até o desenvolvimento da planta adulta. A auxina em particular, desempenha um papel fundamental na formação de um complexo sistema radicular nas plantas. Sabe-se que o transporte polar desse hormônio concentra a auxina em determinados tecidos, desempenhando um papel essencial na expressão diferencial de genes que modulam o desenvolvimento dos vários órgãos da planta. Monocotiledôneas e em particular Poaeceaes exibem um complexo sistema radicular que parece ser chave para o seu vasto potencial adaptativo, mas pouco se sabe sobre os fatores que envolvem as respostas sensoriais e de desenvolvimento que guiam a escolha de quais tipos de raiz as plantas elegem. O objetivo deste estudo foi explorar as vias hormonais e abióticas que influenciam a arquitetura das raízesSetaria viridis has been used as a model organism for grasses with C4 metabolism, seeking to elucidate plant biological processes. The importance of monocotyledons with C4 metabolism is due to better photosynthetic balance when compared to plants with C3 metabolism in climatic conditions with high temperatures, such as those that prevail in Brazil. Setaria viridis represents a model system of great importance for Brazilian agriculture since both the Brazilian production of biofuels and food is strongly related to C4 organisms. Plant hormones are crucial in the establishment of complex organs from zygote to the adult plant development. Auxin in particular, plays a key role in the formation of a complex radicular system in plants. The polar transport of this hormone is known to concentrate auxin in particular tissues, playing an essential roll in the differential expression of genes that will modulate the development of the various plant organs. Monocots and in particular Poaeceae display a complex radicular system that seems to be key for it vast adaptive potential, but little is known about the factors involving the sensing and developmental responses that guide the choice of which root types to elect. The aim of this study was to explore the hormonal and abiotic cues that influence the root architectur
Characterization of a putative phosphatidyl inositol 4-kinase and its effect on pollen grain development
No full textO desenvolvimento dos grãos de pólen está intimamente relacionado à viabilidade dos mesmos e esta pode afetar significativamente o sucesso reprodutivo das plantas. No interior das anteras, as células esporogênicas masculinas se diferenciam e sofrem meiose para produzir micrósporos, que dão origem às unidades independentes de dispersão, os grãos de pólen. Estes mecanismos de desenvolvimento e maturação dos grãos de pólen são influenciados pelo tráfego de vesículas e endomembranas celulares. Desta forma, conhecer os mecanismos moleculares que dirigem e coordenam o desenvolvimento dos grãos de pólen são fundamentais, pois geram informações que podem elucidar o funcionamento e vias regulatórias que levam à diferenciação celular, morfogênese e controle gênico ao longo do desenvolvimento dos grãos de pólen. Na literatura encontra-se a identificação do gene AtPI4K?1(At2g40850), que codifica para uma fosfatidilinositol 4-quinase putativa, predominantemente expressa durante a meiose e a maturação dos grãos de pólen. Estudos ultraestruturais em plantas mutantes para esse gene mostraram grãos de pólen de formato irregular com viabilidade reduzida, indicando possíveis implicações desse produto gênico no desenvolvimento do grão de pólen. O presente trabalho tem como objetivo a caracterização do gene At2g40850 e o estudo de seu envolvimento no desenvolvimento de grãos de pólen. A caracterização comparativa do desenvolvimento de anteras e de pólen por microscopia de luz e eletrônica de transmissão em Arabidopsis thaliana selvagem e mutantes foi realizada, identificando-se em algumas amostras de células de tapete, vacúolos maiores do que nas amostras de material selvagem. Adicionalmente, enquanto anteras do tipo selvagem apresentavam micrósporos circulares vacuolados, anteras mutantes exibiram micrósporos bem desenvolvidos e também micrósporos defeituosos em forma e tamanho, características que podem estar associadas a possíveis defeitos durante a meiose ou a formação de tétrades. Adicionalmente, apesar de não ter sido possível a realização da complementação de mutantes para o gene At2g40850, possivelmente devido à ocorrência de competição gametofítica por grãos de pólen viáveis, os resultados obtidos através de análises de expressão transiente com o auxílio de marcadores de compartimentos celulares (linhas WAVE) em plantas de Nicotiana benthamiana, identificaram a co-localização subcelular da proteína ATPI4K?1 no golgi. Além disso, experimentos envolvendo seleção pelo sistema de duplo híbrido realizadas em amostras de botões florais de A. thaliana, revelaram uma lista de 27 possíveis interatores da proteína codificada pelo gene At2g40850 que podem ser ponto de partida para a elucidação de mecanismos de interação entre proteínas. Por fim, em análises de expressão heteróloga, foi possível obter a expressão da proteína em sistemas bacterianos e a purificação da mesma com alto grau de pureza, mostrando boas perspectivas de estudos futuros para a elucidação da atividade cinásica putativa da proteína ATPI4K?1. As informações geradas neste trabalho podem colaborar para estudos futuros do processo de desenvolvimento de grãos de pólen, aumentando o conhecimento sobre os mecanismos relacionados ao desenvolvimento reprodutivo masculino em plantasThe development of pollen grains is closely related to their viability and can significantly affect the reproductive success of plants. Inside the anthers, male sporogenic cells differentiate and undergo meiosis to produce microspores, which give rise to the independent dispersion units, pollen grains. These mechanisms of pollen grain development and maturation are influenced by the traffic of cellular vesicles and endomembranes. Thus, knowing the molecular mechanisms that direct and coordinate the development of pollen grains are fundamental, as they generate information that can elucidate the functioning and regulatory pathways that lead to cell differentiation, morphogenesis and gene control throughout the development of pollen grains. In the literature there is the identification of the AtPI4K?1 gene (At2g40850), which codes for a putative phosphatidylinositol 4-kinase, predominantly expressed during meiosis and pollen grain maturation. Ultrastructural studies in mutant plants for this gene showed irregularly shaped pollen grains with reduced viability, indicating possible implications of this gene product on pollen grain development. The present work aims to characterize the At2g40850 gene and to study its involvement in pollen grain development. Comparative characterization of anther and pollen development by light microscopy and transmission electron microscopy in wild Arabidopsis thaliana and mutants was performed, identifying in some carpet cell samples larger vacuoles than in wild material samples. In addition, while wild anthers had vacuolated circular microspores, mutant anthers exhibited well-developed microspores as well as defective microspores in shape and size, characteristics that may be associated with possible defects during meiosis or tetrad formation. In addition, although mutant complementation to the At2g40850 gene was not possible, possibly due to the occurrence of gametophytic competition for viable pollen grains, the results obtained through transient expression analysis with the aid of compartiment cell markers (WAVE lines) in Nicotiana benthamiana plants identified the subcellular co-localization of ATPI4K?1 protein in golgi. In addition, experiments involving double hybrid system selection performed on A. thaliana flower bud samples revealed a list of 27 possible protein interactors encoded by the At2g40850 gene that may be the starting point for elucidating protein interaction mechanisms. Finally, in heterologous expression analysis, it was possible to obtain protein expression in bacterial systems and to purify it with high purity, showing good prospects for future studies to elucidate the putative kinetic activity of ATPI4K?1 protein. The information generated in this work may contribute to future studies of the pollen grain development process, increasing the knowledge about the mechanisms related to male reproductive development in plants
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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