1,720,970 research outputs found
Die Bedeutung des zentralen Blatt-Kohlenhydratstoffwechsels von Arabidopsis thaliana für die Interaktion mit Colletotrichum higginsianum
Full text linkHemibiotrophic pathogens interact with host plants in two consecutive phases. An initial biotrophic growth phase inside living host cells is followed by a necrotrophic phase, in which host tissue is sequentially killed. The hemibiotrophic fungus Colletotrichum higginsianum establishes itself through clearly defined infection steps on Arabidopsis thaliana in a compatible interaction. After breaching the host cell wall with an appressorium, the fungus forms intracellular biotrophic hyphae surrounded by the host plasma membrane. Following a short biotrophic phase, leaf tissue is colonized by secondary necrotrophic hyphae accompanied by extensive necrotic lesions on host leaves. In this study, it was shown that carbohydrate availability of Arabidopsis influences susceptibility towards C. higginsianum. Mutants with an impaired starch metabolism experienced faster fungal proliferation and showed increased disease symptoms. Accordingly, the reduced carbohydrate budget and not the duration of carbohydrate shortage increased susceptibility in this interaction. This observation was further supportet by a negative correlation between carbohydrate accumulation in the light and susceptibility towards C. higginsianum. By employing additional genotypes with nocturnal carbohydrate shortage, a clear coincidence between diurnal carbohydrate turnover and susceptibility was corroborated. Analyses of different defense responses revealed that the accumulation of secondary metabolites such as salicylic acid, camalexin and glucosinolates was limited due to reduced carbohydrate availability. Dark-induced carbohydrate shortage in different interaction phases indicated that carbohydrate supply by the host is dispensable during biotrophic growth of C. higginsianum. Furthermore, induced carbohydrate shortage affected susceptibility most during the necrotrophic interaction, indicating that affected defense increases susceptibility especially during necrotrophic colonization. An analysis of cell wall composition demonstrated that periodic carbohydrate shortage in different mutants suffering from nocturnal carbon starvation, caused reduced contents of the monosaccharides arabinose, galactose and galacturonic acid in pectic cell wall matrix polymers. Comparison to described cell wall mutants suggested that the observed cell wall defects reduce penetration resistance to C. higginsianum. In contrast to the increased susceptibility towards C. higginsianum, starchless mutants were more resistant towards the biotrophic powdery mildew fungus E. cruciferarum, which was not due to the observed changes in cell wall composition. Mutagenesis of starchless pgm mutants yielded a mutant population for forward genetic screens. By selecting suppressors of pgm hypersusceptibility, 63 mutants with reduced susceptibility towards C. higginsianum including 8 mutants with pgm-specific resistance could be identified. Selectivity of the screening was proven by the identification of a previously described resistant mutant. Moreover, a mutant showing pgm-specific resistance could be mapped to a 800 kb genomic region on chromosome 3 containing interesting candidate genes for further analyses.Hemibiotrophe Pathogene interagieren mit ihren Wirtspflanzen in zwei zeitlich aufeinanderfolgenden Phasen. In einer initialen biotrophen Phase wachsen die Pathogene innerhalb lebendender Wirtszellen, während das Wirtsgewebe in der nachfolgenden nekrotrophen Phase sequentiell abgetötet wird. Colletotrichum higginsianum ist ein hemibiotropher Pilz, der eine kompatible Interaktion mit Arabidopsis thaliana eingeht und dabei verschiedene klar definierte Infektionsschritte durchläuft. Nachdem die Zellwand des Wirtes mit einem Appressorium durchstoßen wurde, bildet der Pilz intrazelluläre biotrophe Hyphen die von der Plasmamembran der Wirtszelle umgeben sind. Nach einer kurzen biotrophen Phase wird das Blattgewebe von sekundären nekrotrophen Hyphen besiedelt, woraufhin großflächige nekrotische Läsionen auf Blättern der Wirtspflanze entstehen. In dieser Arbeit konnte gezeigt werden, dass die Kohlenhydratverfügbarkeit von Arabidopsis die Suszeptibilität gegenüber C. higginsianum beeinflusst. Mutanten mit einem beeinträchtigten Stärkestoffwechsel wurden schneller durch den Pilz besiedelt und wiesen nach Etablierung der Interaktion stärkere Krankheitssymptome auf. Quantitative Analysen des intrazellulären Pilzwachstums zeigten, dass diese Mutanten unabhängig von der Dauer der Lichtphase eine erhöhte Suszeptibilität gegenüber C. higginsianum aufwiesen. Daraus konnte geschlossen werden, dass nicht die Dauer des Zuckermangels, sondern die Reduktion des Kohlenhydratbudgets die erhöhte Suszeptibilität vermittelt. Dieser Zusammenhang wurde auch durch eine negative Korrelation zwischen der Kohlenhydratakkumulation während der Lichtphase und der Suszeptibilität gegenüber C. higginsianum unterstützt. Durch die Untersuchung weiterer Genotypen mit einem nächtlichen Kohlenstoffmangel konnte eine klare Koinzidenz zwischen dem diurnalen Kohlenhydratumsatz und der Suszeptibilität weiter bekräftigt werden. Analysen verschiedener induzierter Abwehrreaktionen zeigten, dass die Kapazität zur Bildung von Sekundärmetaboliten wie Salicylsäure, Camalexin und Glucosinolaten in stärkefreien Mutanten aufgrund einer reduzierten Kohlenhydratverfügbarkeit vermindert war. Durch Dunkel-induzierten Kohlenhydratmangel während verschiedener Phasen der Interaktion zwischen Arabidopsis und C. higginsianum konnte gezeigt werden, dass der Pilz während des biotrophen Wachstums nicht auf die Versorgung mit Kohlenhydraten durch den Wirt angewiesen ist. Außerdem wirkte sich ein induzierter Kohlenhydratmangel während der nekrotrophen Interaktionsphase besonders stark auf die Suszeptibilität für den Pilz aus. Beeinträchtigungen induzierter Abwehrreaktionen könnten sich folglich besonders während des nekrotrophen Wachstums des Pilzes auf die Suszeptibilität auswirken. Analysen der Zellwandzusammensetzung verschiedener Mutanten mit einem nächtlichen Kohlenhydratmangel zeigten, dass der regelmäßig wiederkehrende Kohlenhydratmangel zu verringerten Gehalten der Monosaccharide Arabinose, Galactose und Galacturonsäure im Pektinanteil der Zellwandmatrix führte. Vergleichende Analysen mit beschriebenen Zellwandmutanten lieferten klare Hinweise, dass dieser Zellwanddefekt die Penetrationsresistenz von Arabidopsis gegen C. higginsianum reduziert. Im Gegensatz zu der erhöhten Suszeptibilität für C. higginsianum hatten stärkefreie Mutanten eine erhöhte Resistenz gegen den obligat biotrophen Mehltaupilz Erysiphe cruciferarum, die nicht durch die beobachteten Zellwandveränderungen begründet war. Durch eine Mutagenese stärkefreier pgm Pflanzen konnte eine Population von Mutanten für vorwärtsgenetische Durchmusterungen erzeugt werden. Durch die Selektion auf Suppressor-Phänotypen der Hypersuszeptibilität von pgm konnten 63 Mutanten mit einer reduzierten Suszeptibilität gegenüber C. higginsianum identifiziert werden, von denen 8 Mutanten eine pgm-spezifische Resistenz zeigten. Durch die Identifizierung einer Mutante, die bereits als resistent beschrieben war, konnte die Selektivität der Durchmusterung belegt werden. Zudem konnte eine Mutante mit pgm-spezifischer Resistenz auf einen 800 kb umfassenden Genombereich von Chromosom 3 kartiert werden, der interessante Kandidatengene für weiterführende Analysen beinhaltet
Loss of the Arabidopsis Protein Kinases ANPs Affects Root Cell Wall Composition, and Triggers the Cell Wall Damage Syndrome
Full text linkThe Arabidopsis NPK1-related Protein kinases ANP1, ANP2 and ANP3 belong to the MAP kinase kinase kinase (MAPKKK) superfamily and were previously described to be crucial for cytokinesis, elicitor-induced immunity and development. Here we investigate the basis of their role in development by using conditional β-estradiol-inducible triple mutants to overcome lethality. In seedlings, lack of ANPs causes root cell bulging, with the transition zone being the most sensitive region. We uncover a role of ANPs in the regulation of cell wall composition and suggest that developmental defects of the triple mutants, observed at the cellular level, might be a consequence of the alterations of the pectic and cellulosic cell wall components. Lack of ANPs also induced a typical cell wall damage syndrome (CWDS) similar to that observed in plants treated with the cellulose biosynthesis inhibitor isoxaben (ISX). Moreover, anp double mutants and plants overexpressing single ANPs (ANP1 or ANP3) respectively showed increased and reduced accumulation of jasmonic acid and PDF1.2 transcripts upon ISX treatment, suggesting that ANPs are part of the pathway targeted by this inhibitor and play a role in cell wall integrity surveillance.Highlights: The loss of ANP function affects cell wall composition and leads to typical cell wall damage-induced phenotypes, such as ectopic lignification and jasmonic acid accumulation
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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