1,720,959 research outputs found
Characterisation of Vigna unguiculata (L.) Walp cultivars and ecotypes from Mozambique by molecular markers
No full textAnálise da expressão e acumulação de DHNs em resposta ao défice hídrico em ecotipos moçambicanos de feijão nhemba (Vigna unguiculata Walp.)
No full textCowpea (Vigna unguiculata (L.) Walp) is a tropical grain legume, which plays an important nutritional role in developing countries of the tropics and subtropics, especially in sub-Saharian Africa, Asia, Central and South America. Its production is limited by a lot of environmental stresses and drought seems to be one of the most important. It has been reported that cowpea has in its genome genes encoding proteins associated with environmental stresses. One of those proteins is a group of proteins called dehydrins. We hypothesized that, as dehydrins have been proposed to protect cellular macromolecules and their expression increase in response to dehydration, it should be used as molecular marker for drought stress tolerance. To test this hypothesis, a fragment of dehydrin was amplified and used for analysis of variability dehydrin gene and cowpea. We used also semi-quantitative RT-PCR (Reverse transcription PCR) to evaluate dehydrin gene expression in plants subjected to water stress. An anti-dehydrin antibody was used to study dehydrin protein accumulation under water stress. Analysis of the dehydrin gene variability revealed a high diversity of this protein family and a high identity to Vigna unguiculata dehydrin presented in database associated to chilling tolerance. Expression of dehydrin was high on the wild ecotypes evidencing more adaptability of this group to water deficit. Western blot analysis revealed an apparent absence of dehydrins in leaves and a presence of a constitutive dehydrin in seeds of unstressed plants
Seed storage protein genes analysis in cowpea (Vigna unguiculata (L.) Walp)
No full textCowpea (Vigna unguiculata (L.) Walp) is one of the most important protein sources in the diet of tropical Africa, Brazil and India. All evidence points to an African origin of V. unguiculata. Development of specific markers is necessary for cultivar identification and protection, and cultivar purity determination. Studies on genetic variation of seed protein composition can be useful in identification of particular genotypes available for the improvement of the protein content and/or the amino acid composition. The major seed storage protein in Leguminosae are globulins that includes legumins, vicilins and lectins. The major component in cowpea is vicilin: a legumin-like globulin is also present. No haemo-agglutinating fractions were detected. Vigna unguiculata accessions collected in different regions of Mozambique were analysed by using vicilin genes. The vicilin genes were amplified from genomic DNA by polymerase chain reaction (PCR) using left and right primers (VICL and VICR) designed by using Phaseolus vulgaris vicilin sequences. The PCR products appeared as 9 bands approximately in a range from 900 to 600 bp. They were cloned using TOPO TA Cloning system. The single insert were selected by PCR colony screening using as primers M13 forward and M13 reverse. Complete sequences were obtained for vicilin genes. Sequence analysis was used to evaluate the vicilin genetic diversity among cowpea and other different Leguminosae species. The DNA sequences were aligned using the Clustal W program and the alignment was slightly manually improved. The ambiguously aligned regions were excluded from the analyses. The analyses allowed the identification of the genetic relationships between different samples from Mozambique ecotypes
Accumulation of dehydrin transcripts in response to water stress in seedlings of Vigna unguiculata
No full textDehydrins are plant proteins produced on the late stages of embryogenesis or in response to dehydrative forces like freezing, salt or water stress or also in response to ABA application. It has been hypothesized that dehydrins play an important role in preserving the structure of cellular macromolecules in plant tissues subjected to desiccation. With the aim of characterizing and studying accumulation of dehydrin transcripts in different organs of Vigna unguiculata seedlings, we isolated by PCR a fragment of dehydrin gene in two ecotypes with different provenience (cultivated and wild ecotypes). The dehydrin fragments were then cloned: positive clones were selected following differences on the molecular weight and sequenced. Expression of dehydrins in different organs, under normal conditions of irrigation and different levels of water stress imposition was evaluated by semi-quantitative RT–PCR. Database search using aminoacidic sequences revealed that inside the cowpea genome there are at least seven members of the multigenic dehydrin family. These members presented a high identity with cowpea clones responsive to dehydration which were correlated to different dehydration stresses. Semi-quantitative RT-PCR revealed that dehydrin transcripts accumulate in all organs except in mature leaves. The accumulation of dehydrin transcripts was significantly different in the two ecotypes at level of roots and hypocotyls. Cultivated ecotypes showed levels of dehydrin transcript accumulation lower than the wild ecotype. Significant differences were not observed on the first leaves
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
Effects of Ozone in Two Differentially Sensitive Poplar Hybrids: Histocytochemical and Molecular Approaches
No full textThe leaf is considered the most sensitive organ to pollution and represents the first target for phyto-toxic action of ozone in sensitive plants. O3 enters the leaf surface via the stomata and induces a hypersensitive-like response (HR) including an oxidative burst and both micro- and macro-scale cell-death. The reactive oxygen species (ROS), generated by O3 dissociation, act non only as damaging agents but mainly as signal molecules for several signal transduction pathways, inducing a range of events interpreted as protective (defence responses).
In order to identify the basis of sensitivity to O3 in arboreal species, we used two poplar hybrids characterized by a different susceptibility to O3 (the ozone sensitive Populus deltoides x maximowiczii, Eridano clone and the more resistant Populus x euoramericana, I-214 clone) exposed to an acute ozone stress: within 24-48 h after the fumigation, only sensitive poplar clone leaves showed the typical dark-black necrosis. The differential sensitivity against acute O3 stress of two poplar hybrids is firstly related to a different equipment of endogenous detoxifying antioxidant enzymes/metabolites and to a differential expression and regulation of specific genes after O3 treatment. The anatomical characteristics of the sensitive poplar hybrid leaves (high stomatal density, low density of mesophyll cell packing) justify its increased sensitivity against ozone stress rather than the tolerant poplar hybrid. These anatomical characteristics can play an important role in O3 uptake, favouring its entrance in mesophyll apoplast and its cyto-toxic activities on mesophyll cells (principally in palisade parenchyma) in the sensitive hybrids. Caryological investigations showed a clear differential response to O3 stress in the two poplar clones: the leaves of the sensitive, sampled during the precocious phases of ozone fumigation, revealed a marked increase in the nuclear/nucleolar functional activity. In the sensitive poplar hybrid O3 induced a rapid accumulation of callose localized in walls around the dying cells, as in response to wounding or pathogen infections. Besides, the rapid and well localized cell death, displayed in O3 sensitive poplar leaves, exhibits some morphological and functional hallmarks of programmed cell death (PCD) processes, as: nuclear and cytoplasm shrinkage, DNA fragmentation, vacuoles lysis, incomplete cell wall breakage and collapse, plasmolysis, persistence of intact organelles until a late stage of deat
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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