1,720,975 research outputs found
Characterization of an alternative symbiotic process between legumes and Bradyrhizobium involving the Type 3 secretion system but not the Nod factor synthesis
No full textLes Bradyrhizobium sont des bactéries du sol ayant la capacité d’établir une interaction symbiotique avec de nombreuses légumineuses. Cette symbiose conduit à la formation d’un nouvel organe, le nodule, au sein duquel la bactérie peut fixer le diazote atmosphérique au bénéfice de la plante. Cette interaction repose largement sur la reconnaissance par la plante de molécules signal,les facteurs Nods (FNs) produits par la bactérie qui contrôlent les processus d’infection et d’organogénèse nodulaire. Récemment, il a été démontré que certaines souches de Bradyrhizobiumnon-photosynthétiques, telles que les souches B. elkanii USDA61 et Bradyrhizobium sp. ORS3257,possèdent la capacité de noduler certaines légumineuses (Glycine max, Aeschynomene indica) enl'absence de facteurs Nods grâce à leur système de sécrétion de type III (T3SS). Cette découverte suggère que certains effecteurs secrétés par cette machinerie de sécrétion, initialement connus pour jouer un rôle dans la répression du système immunitaire de la plante hôte, peuvent directement activer la nodulation en court-circuitant les premières étapes de la voie de signalisation initiée parles FNS. Dans un premier temps, l’objectif principal de ce travail de thèse a consisté à avancer dans la compréhension des mécanismes mis en jeu lors de cette nouvelle interaction FN-indépendante T3SSdépendanteen utilisant la souche ORS3257 en interaction avec la légumineuse tropicale A. indica. Il a été démontré que ce processus symbiotique repose sur un cocktail d'au moins 5 effecteurs quijouent un rôle distinct et complémentaire dans les processus d'infection, d'organogenèse desnodules et de répression de la réponse immune. Plus particulièrement, un nouvel effecteur nucléaire appelé ErnA pour « Effector required for nodulation-A » et largement distribué chez les Bradyrhizobium, a été identifié comme étant le principal inducteur de l’organogenèse nodulaire.Dans un second temps, nous avons mené une analyse génomique comparative sur 146 génomes deBradyrhizobium afin de mieux comprendre la distribution du T3SS et des principaux effecteurs identifiés à ce jours. Il a été mis notamment en évidence que le T3SS est très répandu dans le genreBradyrhizobium et qu’il partage une histoire évolutive commune avec les gènes de nodulation nod. L’ensemble de ce travail de thèse constitue une première étape dans la compréhension des mécanismes moléculaire recrutés pour la mise en place d’un nouveau processus de nodulation indépendante d’une signalisation FNs et suggère, par ailleurs, que le T3SS des Bradyrhizobium pourrait jouer un rôle symbiotique bien plus important qu’estimé jusqu’alors.Bradyrhizobia are soil bacteria able to establish a symbiotic interaction with a wide range oflegume species. This symbiosis leads to the formation of a new organ, the nodule, in which thebacteria can fix atmospheric dinitrogen for the plant’s benefit. This interaction largely depends onthe plant recognition of bacterial signal molecules, the Nod factors (NFs), that control the infectionand nodule organogenesis processes. Recently, it has been demonstrated that some nonphotosyntheticBradyrhizobium strains, such as B. elkanii USDA61 and Bradyrhizobium sp. ORS3257,are capable to nodulate some legumes (Glycine max, Aeschynomene indica) in the absence of NFsand that this capacity is due to their type III secretion system (T3SS). This discovery suggests thatsome effectors secreted by this secretory machinery, initially believed to solely play a role in thesuppression of plant immunity, can directly activate the nodulation by bypassing the early stages ofthe symbiotic signaling pathway activated by the NFs. The main objective of this thesis was toprogress in the understanding of the mechanisms involved in this novel NF-independent T3SSdependentinteraction using as model the interaction of the strain ORS3257 with the tropical legumeA. indica. It has been shown that this symbiotic process relies on a cocktail of at least 5 effectors thatplay distinct and synergistic roles in the processes of infection, nodule organogenesis andsuppression of the plant immune response. In particular, a novel nuclear effector, that we namedErnA for "Effector required for nodulation-A", is widely distributed in the Bradyrhizobium genus andwas identified as the main inducer of nodule organogenesis. In addition, we have conducted acomparative genomic analysis of 146 Bradyrhizobium genomes in order to better understand thedistribution of T3SS and the main effectors identified to date. This showed that the T3SS iswidespread in the Bradyrhizobium genus and shares a common evolutionary history with the nodgenes. This thesis work constitutes a first step in the understanding of the molecular mechanismsinvolved in this NF-independent T3SS-dependent nodulation and suggests that the T3SS ofbradyrhizobia could play a much larger symbiotic role than originally thought
Caractérisation d’un processus symbiotique alternatif entre légumineuses et Bradyrhizobium impliquant le système de sécrétion de type 3 (T3SS) mais pas la synthèse de facteurs Nods
No full textBradyrhizobia are soil bacteria able to establish a symbiotic interaction with a wide range oflegume species. This symbiosis leads to the formation of a new organ, the nodule, in which thebacteria can fix atmospheric dinitrogen for the plant’s benefit. This interaction largely depends onthe plant recognition of bacterial signal molecules, the Nod factors (NFs), that control the infectionand nodule organogenesis processes. Recently, it has been demonstrated that some nonphotosyntheticBradyrhizobium strains, such as B. elkanii USDA61 and Bradyrhizobium sp. ORS3257,are capable to nodulate some legumes (Glycine max, Aeschynomene indica) in the absence of NFsand that this capacity is due to their type III secretion system (T3SS). This discovery suggests thatsome effectors secreted by this secretory machinery, initially believed to solely play a role in thesuppression of plant immunity, can directly activate the nodulation by bypassing the early stages ofthe symbiotic signaling pathway activated by the NFs. The main objective of this thesis was toprogress in the understanding of the mechanisms involved in this novel NF-independent T3SSdependentinteraction using as model the interaction of the strain ORS3257 with the tropical legumeA. indica. It has been shown that this symbiotic process relies on a cocktail of at least 5 effectors thatplay distinct and synergistic roles in the processes of infection, nodule organogenesis andsuppression of the plant immune response. In particular, a novel nuclear effector, that we namedErnA for "Effector required for nodulation-A", is widely distributed in the Bradyrhizobium genus andwas identified as the main inducer of nodule organogenesis. In addition, we have conducted acomparative genomic analysis of 146 Bradyrhizobium genomes in order to better understand thedistribution of T3SS and the main effectors identified to date. This showed that the T3SS iswidespread in the Bradyrhizobium genus and shares a common evolutionary history with the nodgenes. This thesis work constitutes a first step in the understanding of the molecular mechanismsinvolved in this NF-independent T3SS-dependent nodulation and suggests that the T3SS ofbradyrhizobia could play a much larger symbiotic role than originally thought.Les Bradyrhizobium sont des bactéries du sol ayant la capacité d’établir une interaction symbiotique avec de nombreuses légumineuses. Cette symbiose conduit à la formation d’un nouvel organe, le nodule, au sein duquel la bactérie peut fixer le diazote atmosphérique au bénéfice de la plante. Cette interaction repose largement sur la reconnaissance par la plante de molécules signal,les facteurs Nods (FNs) produits par la bactérie qui contrôlent les processus d’infection et d’organogénèse nodulaire. Récemment, il a été démontré que certaines souches de Bradyrhizobiumnon-photosynthétiques, telles que les souches B. elkanii USDA61 et Bradyrhizobium sp. ORS3257,possèdent la capacité de noduler certaines légumineuses (Glycine max, Aeschynomene indica) enl'absence de facteurs Nods grâce à leur système de sécrétion de type III (T3SS). Cette découverte suggère que certains effecteurs secrétés par cette machinerie de sécrétion, initialement connus pour jouer un rôle dans la répression du système immunitaire de la plante hôte, peuvent directement activer la nodulation en court-circuitant les premières étapes de la voie de signalisation initiée parles FNS. Dans un premier temps, l’objectif principal de ce travail de thèse a consisté à avancer dans la compréhension des mécanismes mis en jeu lors de cette nouvelle interaction FN-indépendante T3SSdépendanteen utilisant la souche ORS3257 en interaction avec la légumineuse tropicale A. indica. Il a été démontré que ce processus symbiotique repose sur un cocktail d'au moins 5 effecteurs quijouent un rôle distinct et complémentaire dans les processus d'infection, d'organogenèse desnodules et de répression de la réponse immune. Plus particulièrement, un nouvel effecteur nucléaire appelé ErnA pour « Effector required for nodulation-A » et largement distribué chez les Bradyrhizobium, a été identifié comme étant le principal inducteur de l’organogenèse nodulaire.Dans un second temps, nous avons mené une analyse génomique comparative sur 146 génomes deBradyrhizobium afin de mieux comprendre la distribution du T3SS et des principaux effecteurs identifiés à ce jours. Il a été mis notamment en évidence que le T3SS est très répandu dans le genreBradyrhizobium et qu’il partage une histoire évolutive commune avec les gènes de nodulation nod. L’ensemble de ce travail de thèse constitue une première étape dans la compréhension des mécanismes moléculaire recrutés pour la mise en place d’un nouveau processus de nodulation indépendante d’une signalisation FNs et suggère, par ailleurs, que le T3SS des Bradyrhizobium pourrait jouer un rôle symbiotique bien plus important qu’estimé jusqu’alors
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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