Entretien avec Jean-Paul Amat

Jean Paul Amat est professeur de biogéographie à l’Université Paris IV-Sorbonne. Ses recherches portent sur la géographie des forêts, les relations entre milieux forestiers et sociétés, la géographie historique. Le croisement entre sa spécialité d’origine, la biogéographie historique, et l’histoire de la Première Guerre Mondiale l’a amené à s’intéresser au rôle stratégique de la forêt et à la question des boisements post-conflit. Ces recherches l’ont conduit à développer des réflexions sur la..

Les géographes et le patrimoine

Le patrimoine : l’émergence d’un objet dans les champs de recherche des géographes, révélateur d’une géographie conçue comme science de l’espace des sociétés Le patrimoine est devenu un objet commun des géographes. Dans un article de 2007, Vincent Veschambre montre clairement l’émergence des problématiques patrimoniales dans la géographie française contemporaine durant les années 1990, tout en soulignant l’entrée tardive et décalée des géographes dans « le concert patrimonial » par rapport à ..

La pagode vietnamienne de Linh Son à Joinville-le-Pont

Cet article est une contribution à la géographie des religions à travers l’analyse de la pagode vietnamienne de Joinville-le-Pont. La pagode, dont on étudie le processus d’implantation et l’organisation intérieure, traduit les stratégies d’adaptation de communautés en exil à un nouveau contexte géographique. L’étude de la fonction symbolique et sociale de ce lieu de culte, permet de mettre en évidence l’organisation matérielle et spatiale d’un courant religieux minoritaire en France et apporte des éléments de compréhension sur le rôle symbolique de certains lieux au sein des diasporas. Enfin, l’analyse du rayonnement de la pagode montre qu’elle se trouve au cœur d’une construction territoriale fondée sur les réseaux plus que sur un mode de regroupement spatial de type paroissial.This article is a contribution to the geography of religions through the analysis of the vietnamese pagoda of Joinville-le-Pont. This pagoda, with its establishing process and its inner organization, shows the strategies for the community in exile to adapt itself to a new geographical context. The study of the symbolic and social role of this worship place under/ines the material and spacial organization of a minority religious group and helps to understand the symbolic role of this kind of places within diasporas. Finally, the study of the pagoda influence shows that it is at the center of a territorial structure based more on networks than on a mode of spacial regrouping, on the type of parish groups

Penser la ville et l’urbain, les paradoxes de la géographie française

La ville, l’urbain sont des notions qui renvoient à des lieux et à des aires, à des sociétés inscrites territorialement, à des formes spatiales, à des paysages, à des polarisations et à des distances particulières. Aussi, la ville et l’urbain constituent-ils logiquement des objets de la géographie. L’expression « géographie urbaine » utilisée par Jean Bruhnes en 1900 est ainsi antérieure à celui de « sociologie urbaine » (1930) voire de « géographie rurale » (1960). La géographie urbaine, cha..

Introduction

Ce numéro de Géographie et cultures se propose d’explorer les dimensions spatiales des mémoires, envisagées à la fois comme un ensemble de modalités et un agence­ment de convocations du passé dans le présent. Ces trente dernières années ont été riches en recherches sur la question des mémoires (Klein, 2000 ; Radstone, 2000 ; Zelizer, 1995 ; Nicolas, 2014), de leurs usages et mésusages (Lavabre, 2000), en histoire bien évidemment (Nora, 1984-1992 ; Assmann, 1995 ; Offenstadt, 1999), mais aussi..

RIG-I plays a dominant role in the induction of transcriptional changes in Zika virus-infected cells and protects from virus-induced cell death

The Zika virus (ZIKV) has received much attention due to an alarming increase in cases of neurological disorders including congenital Zika syndrome associated with infection. To date, there is no effective treatment available. An immediate response by the innate immune system is crucial for effective control of the virus. Using CRISPR/Cas9-mediated knockouts in A549 cells, we investigated the individual contributions of the RIG-I-like receptors MDA5 and RIG-I to ZIKV sensing and control of this virus by using a Brazilian ZIKV strain. We show that RIG-I is the main sensor for ZIKV in A549 cells. Surprisingly, we observed that loss of RIG-I and consecutive type I interferon (IFN) production led to virus-induced apoptosis. ZIKV non-structural protein NS5 was reported to interfere with type I IFN receptor signaling. Additionally, we show that ZIKV NS5 inhibits type I IFN induction. Overall, our study highlights the importance of RIG-I-dependent ZIKV sensing for the prevention of virus-induced cell death and shows that NS5 inhibits the production of type I IFN

Pitfall trap sampling bias depends on body mass, temperature, and trap number: insights from an individual-based model

The diversity and community composition of ground arthropods is routinely analyzed by pitfall trap sampling, which is a cost- and time-effective method to gather large numbers of replicates but also known to generate data that are biased by species-specific differences in locomotory activity. Previous studies have looked at factors that influence the sampling bias. These studies, however, were limited to one or few species and did rarely quantify how the species-specific sampling bias shapes community-level diversity metrics. In this study, we systematically quantify the species-specific and community-level sampling bias with an allometric individual-based model that simulates movement and pitfall sampling of 10 generic ground arthropod species differing in body mass. We perform multiple simulation experiments covering different scenarios of pitfall trap number, spatial trap arrangement, temperature, and population density. We show that the sampling bias decreased strongly with increasing body mass, temperature, and pitfall trap number, while population density had no effect and trap arrangement only had little effect. The average movement speed of a species in the field integrates body mass and temperature effects and could be used to derive reliable estimates of absolute species abundance. We demonstrate how unbiased relative species abundance can be derived using correction factors that need only information on species body mass. We find that community-level diversity metrics are sensitive to the particular community structure, namely the relation between body mass and relative abundance across species. Generally, pitfall trap sampling flattens the rank-abundance distribution and leads to overestimations of ground arthropod Shannon diversity. We conclude that the correction of the species-specific pitfall trap sampling bias is necessary for the reliability of conclusions drawn from ground arthropod field studies. We propose bias correction is a manageable task using either body mass to derive unbiased relative abundance or the average speed to derive reliable estimates of absolute abundance from pitfall trap sampling

Les "pôles secondaires" dans la réorganisation des mobilités : maturité et durabilité des espaces périurbains ?

International audienceCette recherche faisait l'hypothèse que les mobilités des habitants des zones périurbains se recomposaient à partir de polarités nouvelles ou plus anciennes, de tailles différentes, dans un espace où cohabitent diverses formes de développement urbain.Ces recompositions seraient par ailleurs, renforcées par une diversification des sociétés locales, une inflexion des comportements de mobilité, et une montée en compétence des acteurs locaux. In fine, il s'agissait dans cette recherche, d'interroger les préjugés pesant sur ces espaces dits "périurbains"

The Enigma of the Respiratory Chain Supercomplex

Respiratory chain dysfunction plays an important role in human disease and aging. It is now well established that the individual respiratory complexes can be organized into supercomplexes, and structures for these macromolecular assemblies, determined by electron cryo-microscopy, have been described recently. Nevertheless, the reason why supercomplexes exist remains an enigma. The widely held view that they enhance catalysis by channeling substrates is challenged by both structural and biophysical information. Here, we evaluate and discuss data and hypotheses on the structures, roles, and assembly of respiratory-chain supercomplexes and propose a future research agenda to address unanswered questions.N.G.L. receives support from the Max Planck Society, the Swedish Research Council (2015-00418), and the Knut and Alice Wallenberg foundation. J.H. and J.N.B. are supported by The Medical Research Council (U105663141 to J.H.)

Assembly mechanism and cryoEM structure of RecA recombination nucleofilaments from Streptococcus pneumoniae

Abstract RecA-mediated Homologous Recombination (HR) is a key mechanism for genome maintenance and plasticity in bacteria. It proceeds through RecA assembly into a dynamic filament on ssDNA, the presynaptic filament, which mediates DNA homology search and ordered DNA strand exchange. Here, we combined structural, single molecule and biochemical approaches to characterize the ATP-dependent assembly mechanism of the presynaptic filament of RecA from Streptococcus pneumoniae ( Sp RecA), in comparison to the Escherichia coli RecA ( Ec RecA) paradigm. Ec RecA polymerization on ssDNA is assisted by the Single-Stranded DNA Binding (SSB) protein, which unwinds ssDNA secondary structures that block Ec RecA nucleofilament growth. We report that neither of the two paralogous pneumococcal SSBs could assist Sp RecA polymerization on ssDNA. Instead, we found that the conserved RadA helicase promotes this Sp RecA nucleofilamentation in an ATP-dependent manner. This allowed us to solve the atomic structure of such a long native Sp RecA nucleopolymer by cryoEM stabilized with ATPγS. It was found to be equivalent to the crystal structure of the Ec RecA filament with a marked difference in how RecA mediates nucleotide orientation in the stretched ssDNA. Then, our results show that Sp RecA and Ec RecA HR activities are different, in correlation with their distinct ATP-dependent ssDNA binding modes