1,721,008 research outputs found
Untersuchung des Zystennematodenresistenzgens Hs4 in unterschiedlichen genomischen Hintergründen
Get PDFMy work consisted of four work packages. In the first, I screened a large set of Patellifolia and Beta species for Hs4 homologs. All Patellifolia species contained highly similar Hs4 homologs, while BvHs4 homologs were present in all Beta species analyzed. When examining the expression patterns of the homologs, I identified substantial differences between species, however, no response to nematode inoculation was observable. In my second work package, I characterized Arabidopsis T3 lines expressing Hs4 from different promoters. I found lines exhibiting significant nematode resistance compared to the susceptible control under in vitro conditions. The resistance was correlated with the Hs4 expression level. In the third work package, I analyzed the ultrastructure of syncytia in high-expressing Hs4-transgenic Arabidopsis lines. Syncytia in non-transgenic Arabidopsis were filled with dense cytoplasm, many functional mitochondria, small vacuoles, and numerous smooth ER vesicles. In contrast, in the resistant roots, necrosis of the initial syncytial cell started five days post-inoculation and completely degraded syncytia were detectable three days later. The cytoplasm was filled with large, translucent membranous structures and vacuoles. Most strikingly, I observed spherical ER-derived membrane aggregations with ribosomes on the outer tubules, while smooth ER was almost completely absent. It can be assumed that the rhomboid-protease Hs4, upon attack by the nematode, leads to the membrane aggregation formation. Rapeseed is a good host for H. schachtii, and the generation of BCN-resistant rapeseed could facilitate crop rotation systems with sugar beet in the future. Therefore, I transformed rapeseed with a 35S::Hs4 construct. I obtained one transgenic plant, and seeds were harvested for future studies
Evolution Quantitativer Krankheitsresistenz gegen Nekrotrophe Schaderreger in Solanum Spezies.
Get PDFGeneralist necrotrophic pathogens like Sclerotinia sclerotiorum threaten many crops worldwide. The absence of complete resistance has driven breeders to rely on quantitative disease resistance (QDR), an incomplete yet broad-range plant defence. However, challenges in linking QDR loci to phenotypes highlight how poorly host regulatory factors are understood. In this thesis, I characterised the QDR diversity of wild tomato populations against S. sclerotiorum. I observed an astonishing diversity of the QDR mechanisms, including infection frequency, lag phase duration, and lesion doubling time (LDT), among and within different species. Using high-throughput phenotyping, I found no correlation between either of the three mechanisms, suggesting the existence of independent biological processes determining QDR. I investigated the shifts in gene expression of genotypes spanning an LDT gradient. Using differential gene expression analysis and different types of network analysis, I observed that basal and highly species-specific gene regulatory networks (GRN) determine LDT-driven QDR. I showed that the conserved NAC29 transcription factor co-opted a role in QDR in Solanum pennellii. Although NAC29 is conserved across all five species, it is only induced upon infection in S. pennellii and is linked to defence-related downstream genes, indicating GRN rewiring. This study demonstrates that complex regulatory rewiring underlies QDR, with lag-phase duration and lesion doubling time (LDT) controlled independently by the host. Evolutionary analysis highlights the role of paralog diversification, followed by lineage-specific co-option into QDR-related gene regulatory networks. These insights improve our understanding of how QDR mechanisms are regulated and evolve, thereby supporting the development of pre-breeding strategies for more effective QDR-focused breeding programs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
The molecular participants of the defense response to the necrotrophic fungus Alternaria alternata on cultivated and wild tomato
Get PDFTomato (Solanum lycopersicum L.) is one of the world’s most valuable vegetable crops, but its production is increasingly threatened by fungal pathogens—particularly Alternaria spp., which cause early blight and brown spot disease complex (EBDC). These necrotrophic fungi kill host tissue and thrive under changing climate conditions, leading to major yield losses and widespread fungicide use. Current cultivars lack strong genetic resistance, making the development of durable, sustainable defense strategies an urgent agricultural priority. We used gene regulatory networks (GRNs) and weighted gene co-expression network analysis (WGCNA) to analyze the transcriptional landscape of resistance to EBDC. This dissertation addresses this challenge by investigating resistance to EBDC through a multi-scale lens, combining quantitative phenotyping, network biology, and wild tomato diversity. It focuses on Solanum chilense, a wild relative of the cultivated tomato. Notably, resistant genotypes exhibited strong transcriptional activity and early activation of defense modules, while susceptible genotypes showed weak, fragmented networks. Temporal network rewiring and module preservation analyses further emphasized that effective resistance relies not just on the presence of defense genes but on their dynamic regulatory coordination. We used high-throughput quantitative phenotyping to capture subtle differences in infection progression across 124 S. chilense accessions. By leveraging phenotypic diversity to resolve resistant/susceptible gene network topologies, this dissertation advances both the understanding of necrotrophic pathogen resistance and the tools available to improve it. The findings highlight S. chilense as a rich source of resistance alleles and demonstrate the potential of systems biology to breed crops with resilience to complex pathogens in the future
Variations on the Author
Get PDF“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
Get PDFWe 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
Elucidating the Mechanisms of Organic Phosphorus Use Efficiency (PoUE) in Symbiotically Grown Vicia faba L. Plants
Get PDFThe use of organic P (Po) is consistently proposed as a possible alternative to lessen the overdependence on chemical P fertilizers in contemporary agricultural systems. Therefore, this study seeks to comprehensively elucidate the mechanisms underlying organic phosphorus use efficiency (PoUE) in nodulating Vicia faba plants. The experiments were carried out in both soil and hydroponics to elucidate the various mechanisms facilitating organic P use efficiency (PoUE) in diverse varieties of Vicia faba plants grown symbiotically under greenhouse and climate chamber conditions with three P sources, viz., phytic acid (Po), KH2PO4 (Pi), and no-P (low KH2PO4-LPi) and inoculated with Rhizobium leguminosarum. The results indicate that plants supplied with Po and Pi produced equivalent amounts of overall dry biomass, with both varying statistically from the no-P treatment. Despite accumulating statistically similar dry biomass, P uptake by Pi-treated plants was 2-fold higher relative to Po-treated plants, highlighting the competent utilization of Po substrate by Vicia faba plants. Po-treated plants did not only exhibit similar growth traits, but also accumulated the highest Pi and malate (carbon) required for the functioning nodules to enhance N2-fixation and P homeostasis relative to the +Pi-treated plants. The results persistently show that Po-treated plants didn’t only increase phosphatases and N-assimilation enzyme activities, but also caused transcriptional upregulation of all plasma membrane (PM) H+-ATPase gene isoforms (VfHA 2, 4,5) in root, nodule, and leaf. The results showed a significant correlation between phosphatase activities and expression of PM H+-ATPase gene isoforms, highlighting synergistic interactions which improved Pi uptake in Po-treated plants symbiotically.The study provides insight into the mechanisms of PoUE
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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