1,720,973 research outputs found
Molecular dissection of the TMV-encoded p126 protein in suppression of virus-induced gene silencing
No full text轉錄後基因靜默（post-transcriptional gene silencing，PTGS），亦即RNA干擾現象 (RNAi)，會導致目標基因的mRNA被分解，是為一種調節基因表現的機制。近幾年來有許多研究顯示，此現象不但廣泛地存在於生物界，更為真核生物用以抵禦病毒侵染的一套固有防禦機制。然而，病毒也演化出另一種反防禦策略，亦即利用抑制子 (suppressor)，去干擾內生的基因靜默訊息傳遞路徑，以達到成功感染目的。本研究以煙草鑲嵌病毒 (TMV) 為模式，探討TMV p126蛋白如何參與對抗PTGS。首先以GFP煙草轉植株 (Nicotiana benthamiana, line 16c) 建立篩選平台，藉由農桿菌接種法 (agroinfiltration) 送入外來GFP，啟動PTGS機制導致16c中GFP mRNA量降低。我們首先觀察到當煙草株遭受TMV感染，或單獨表現p126蛋白時，GFP不僅可恆常表現，甚至有被助長表現之情況。進一步將p126蛋白依據其不同的功能性區塊 (domain) 進行擷取，共分為methyltransferase (MET)、non-conserved region (nonI)、non-conserved region II (nonII) 和helicase (HEL) 四個區塊。當個別表現MET、nonII和HEL於16c時，皆顯示其有抑制PTGS之功能。為了進一步釐清其參與機制，我們利用點突變破壞MET及HEL之酵素活性區，但結果顯示其酵素功能似乎不參與在抑制PTGS之機制中。令人驚訝的是，當我們替換nonII三個會影響病徵之胺基酸後，便失去抑制PTGS之功能。另外，我們也建立p126煙草轉殖株，期望找出病毒致病性與PTGS抑制功能兩者之間的相關連結，但若要明確了解整個機制則仍有待持續的研究與探討。Post-transcriptional gene silencing (PTGS) is a conservative phenomenon across kingdoms. In plants, it has been demonstrated that PTGS functions as an intrinsic defense mechanism during viral infection. On the other hand, viruses have evolved counter-defense strategies by encoded suppressors to circumvent PTGS. In previous studies, Tobacco mosaic virus (TMV) encoded p126 protein has been exhibited as a suppressor of PTGS although its mechanism remains unknown. In this current study, we found that there are multiple suppressor domains/motifs within the p126 protein, including methyltransferase, helicase and non-conserved region II, implicating that these domains/motifs could function synergistically against PTGS. Nevertheless, these suppressor domains might exhibit differential consequences on local and/or systemic gene silencing. Moreover, the enzymatic activities of methyltransferase and helicase are dispensable in the suppression pathways. Interestingly, several amino acids within the non-conserved region II pivotal for pathological consequence seem to intimately correlate with extend of the ability of gene silencing suppression. Together, these results suggest that a role of gene silencing suppression of TMV determinates its susceptibility on host plants. Furthermore, the MAPK signal cascade(s) was involved in the functioning of the p126-mediated gene silencing in tobacco. Our findings will therefore help elucidate the function and evolution of different virus suppressor and lead to new crop protection strategies.口試委員會審定書………………………………………………………………….. I
Abstract…………………………………………………………………………........ II
中文摘要…………………………………………………………………………… IV
Content of figures
Figure 1. The map of constructs used in this study. ………………………….………... 30
Figure 2. Suppression of PTGS by TMV……………………...……………………. 32
Figure 3. Effects of p126 on systemic GFP silencing………..……………..…………… 34
Figure 4. The different p126 fragments are associated with suppressor activity…………... 37
Figure 5. Transient expression of mutant variants of p126 in N. benthamiana p126 mutate variants………………………………………………………………………………….…..… 39
Figure 6. The phenotype of MII-16………………………………………………….………. 41
Figure 7. MAPKs were affected by TMV infection and overexpression of the p126 protein... 43
Content of tables
Table 1. Primers sequences used in this study………………………………………………….45
Table 2. Statistics of systemic silencing suppression by the TMV p126 and others suppressors…………………………………………………………………………………….47
Table 3. Suppression of systemic silencing by TMV p126 and other mutants………………………………………………………………………………………….48
Introduction……………………………………………………………………….. 1
RNA silencing…………………………………………………………….……. 1
RNA silencing pathway…………………………………………………………. 2
Viral suppressors of RNA silencing …………………………………………… 4
Diverse mechanisms of viral suppressors affect RNA silencing……………….. 4
RNA silencing suppressor encoded by TMV………………..…………….……. 6
Materials and Methods …………………………………………………………... 10
Plant material and growth conditions…………………………………………. 10
Plasmid constructs…………………………………………………………….. 10
Agrobacterium mediated the induction of systemic GFP silencing…………….. 12
GFP image of plants under UV illumination………………………………..…... 12
Analysis of proteins extracted from infiltrated N. benthamiana (16c) leaves by pull-down western blotting……………………………………………………. 13
RT-PCR……………………………………………………………………...... 14
Northern blot analysis ………………………………………………………… 15
Results ……………………………………………………………….…………... 17
Suppression of PTGS by TMV………………………………………………... 17
The TMV-encoded p126 protein involves in the PTGS suppression……..…... 18
Dissection of the TMV-encoded p126 protein in the suppression of PTGS….. 19
The enzymatic activities of the p126 are negligible on the PTGS suppression.... 21
Mutational analysis of the non-conserved region II in the PTGS suppression…. 22
The TMV-encoded p126 suppressor affects the MAPK signal transduction…… 24
Discussion………………………………………………………………………...... 25
Figures……………………………………………………………………………. 30
Tables……………………………………………………………………………... 45
References…………………………………………………………………….….. 49
Appendix…………………………………………………………………………. 67
Generation of the p126 transgenic tobacco plants…………………………. 6
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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