1,720,956 research outputs found
Comparative epigenomic and transcriptomic analysis of Populus roots under excess Zn
No full textEpigenetic modifications of chromatin structure are extremely important in mediating stress responses in plants. Epigenetic modifications are especially important in perennial species such as trees, where they contribute to phenotypic plasticity and adaptation to unfavourable environments. Populus is a model for physiological studies of trees, and is suitable for phytoremediation of Zn-contaminated soils. Currently, epigenetic modifications involved in Zn stress response are poorly characterized for Populus. Here, we compared changes in epigenetic modifications under excess Zn using chromatin immunoprecipitation sequencing (Chip-Seq) for two histone modifications associated with highly expressed genes (H3K4me3) and repressed genes (H3K27me3) in roots of Populus × canadensis I-214. Chip-Seq data were integrated with RNA-Seq transcript abundance data to examine how epigenetic modifications affect gene expression. These analyses showed that genes with a H3K4me3 modification are generally high-expressed, while genes with a H3K27me3 modification on the 5′-UTR are mainly low-expressed. H3K4me3 modifications in roots under excess Zn condition were enriched in genes involved in carbon (C) catabolism, nitrogen (N) metabolism, and in regulation of sub-cellular vesicular trafficking. These results are consistent with Zn redistribution at a sub-cellular level to buffer Zn-induced nutrient imbalance and osmotic stress in Zn-stressed roots. In contrast H3K27me3 modifications were enriched primarily in genes involved in photosynthetic processes. Together our results provide a useful resource for understanding epigenetic modifications in response to excess Zn in Populus roots, and constitute a starting point for the identification of epigenetic markers and improving phytoremediation potential in this species
The Genetic Regulation of Wood Vessel Anatomical Traits in Populus
Full text linkAbstractVessel elements are highly lignified, tube-like cells that serve as the primary water transporting conduits in angiosperm wood. These cells stack end-on-end to form larger structures known as vessels, which provide a low-resistance pathway for the movement of water from roots to leaves. The dimensions and distribution of vessels in wood (vessel anatomy) directly influence water transport efficiency, ultimately affecting tree photosynthetic capacity and growth. Vessel anatomy is also a factor that contributes to the vulnerability of trees to drought-induced cavitation, a process that can lead to lethal hydraulic failure. The genetic regulation of wood anatomy and related physiological traits is not very well understood. A detailed review of wood structure, function, drought acclimation, and implications for forest tree survival can be found in Chapter 1 of this dissertation. Chapters 2 to 4 consist of three studies that make use of a unique Populus deltoides × nigra pedigree carrying genomically defined insertions and deletions that generate gene dosage variation. In Chapter 2, we found that all examined wood traits are under genetic control, showing moderate heritabilities ranging from 0.32 to 0.53. We found significant line-dependent trait variation and significant correlations between most examined traits and gene dosage at specific genomic regions. In Chapter 3, we studied whole transcriptome gene expression in wood forming tissues and integrated our analyses with our previous trait-dosage correlations to find putative mechanisms and specific candidate genes related to trait variation. In particular, we found evidence for tree height-independent regulation of vessel traits. Lastly, in Chapter 4 we found evidence of gene dosage-dependent variation in vessel anatomy-related physiological traits, including vulnerability to drought-induced cavitation. Understanding the genetic regulation of vessel traits in wood will be vital for the development of successful mitigation strategies under current and future climate change-related drought
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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