1,720,962 research outputs found
Luminol-based Assay for Detection of Immunity Elicitor-induced Hydrogen Peroxide Production in Arabidopsis thaliana Leaves
Full text linkIn Arabidopsis thaliana, one of the very early immune-related responses induced after elicitor perception is the oxidative burst, i.e. reactive oxygen species (ROS) generation including superoxide anion and hydrogen peroxide (H2O2). ROS production plays different roles in a wide range of biotic and abiotic stress responses, including the closure of stomata and the regulation of cell expansion. In particular, elicitor-induced H2O2 is produced mainly by the membrane localized NAD(P)H oxidases RESPIRATORY BURST OXIDASE HOMOLOGUE D and F. In this protocol, we describe a simple and reproducible luminol/peroxidase-based assay to detect and evaluate immunity-related accumulation of H2O2 produced in Arabidopsis leaf discs treated with immunity elicitors, such as oligogalacturonides (OGs), flagellin (flg22) or the elongation factor-thermo-unstable (EF-Tu - elf18). This method is based on the detection of the luminescence released by excited-luminol molecules generated after the horseradish peroxidase (HRP)-catalyzed oxidation of luminol molecules in the presence of H2O2. Levels as well as duration of the luminescence are proportional to the amount of H2O2 produced by elicited leaf discs
Ethylene production in Botrytis cinerea- and oligogalacturonide - induced immunity requires calcium-dependent protein kinases
No full textPlant immunity against pathogens is achieved through rapid activation of defense responses that occur upon sensing of microbe- or damage-associated molecular pattern, respectively referred to as MAMPs and DAMPs. Oligogalacturonides (OGs), linear fragments derived from homogalacturonan hydrolysis by pathogen-secreted cell wall-degrading enzymes, and flg22, a 22-amino acid peptide derived from the bacterial flagellin, represent prototypical DAMPs and MAMPs, respectively. Both types of molecules induce protection against infections. In plants, like in animals, calcium is a second messenger that mediates responses to biotic stresses by activating calcium-binding proteins. Here we show that simultaneous loss of calcium-dependent protein kinases (CDPKs) CPK5, CPK6 and CPK11 affects Arabidopsis thaliana basal as well as elicitor- induced resistance to the necrotroph Botrytis cinerea, by affecting pathogen-induced ethylene production and accumulation of the ethylene biosynthetic enzymes 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 2 (ACS2) and 6 (ACS6). Moreover, ethylene signaling contributes to OG-triggered immunity activation, and lack of CPK5, CPK6 and CPK11 affects the duration of OG- and flg22-induced gene expression, indicating that these kinases are shared elements of both DAMP and MAMP signaling pathways. This article is protected by copyright. All rights reserved
Camalexin Quantification in Arabidopsis thaliana Leaves Infected with Botrytis cinerea
Full text linkPhytoalexins are heterogeneous low molecular mass secondary metabolites with antimicrobial activity produced in response to pathogen invasion attempts at the infection site and represent an important part of the plant defense repertoire. Camalexin (3-Thiazol-2′-yl-indole) is a known phytoalexin first detected and isolated in Camelina sativa, from which it takes its name, infected with Alternaria brassicae (Browne et al., 1991). Production of camalexin is also induced in Arabidopsis thaliana leaves by a range of biotrophic and necrotrophic plant pathogens (bacteria, oomycetes, fungi and viruses) (Ahuja et al., 2012) as well as by abiotic stresses, such as UV and chemicals (e.g. acifluorfen, paraquat, chlorsulfuron and α-amino butyric acid) (Zhao et al., 1998; Tierens et al., 2002). Camalexin originates from tryptophan and CYP79B2 and CYP71B15 (PAD3) are P450 enzymes that catalyze important steps in its biosynthetic pathway (Glawischnig, 2007). In this protocol the detection and quantification of camalexin produced in Arabidopsis leaves infected with the necrotrophic fungus Botrytis cinerea is described
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
Immune responses induced by oligogalacturonides are differentially affected by AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2
Full text linkDispelling 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
- …
