13 research outputs found

    Deep-sea sediments texture and magnetic fabric, indicators of bottom currents regime

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    Critical speeds for erosion, transport and deposition of sedimentary particles and prevailing bottom currents intensities are in such a range that the textural properties of the sediment silt fraction may be correlated to the intensity of the deep circulation. On the other hand, the long axis of the sediment magnetic susceptibility ellipsoid, should be aligned according to the current flow. These hypotheses have been positively tested in five abyssal areas. The authors then apply textural studies to the study of Cenozoic deep water circulation in two continental margin areas (Bay of Biscay and Western mediterranean, DSDP Site 400 and Site 372). The results are in good agreement with informations provided by micropaleontological and geochemical indicators. [NOT CONTROLLED OCR]Les conditions d'érosion, de transport et de dépôt des particules sédimentaires et la gamme des vitesses des courants de fond susceptibles de prévaloir en milieu abyssal sont telles que les propriétés texturales de la fraction silteuse des sédiments paraissent pouvoir être corrélées a l'intensité de la circulation profonde. D'autre part, le grand axe de l'ellipsoïde des indices de susceptibilité magnétique des sédiments paraît s'aligner selon la direction du courant prévalant a l'interface. Un test de ces hypothèses dans cinq secteurs de la zone abyssale apparaît positif. Les auteurs appliquent la première de ces techniques (texture) a l'étude de l'évolution de la circulation profonde au cours du Tertiaire dans deux sites des marges continentales (golfe de Gascogne et Méditerranée occidentale, DSDP sites 400 et 372). L'évolution mise en évidence est en accord avec les informations fournies par les indicateurs géochimiques et micropaléontologiques. [OCR NON CONTRÔLE

    Mesures et modèles conductifs

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    Mesures et modèles thermiques sont combinés pour tendre vers une ébauche réaliste de la distribution du champ de température en bassins sédimentaires. Les résultats des travaux en cours, sur le Bassin parisien, sont présentés : - acquisition des données dans les forages géothermiques, - corrélation entre puits et synthèse des résultats, - modèles de comportement thermique du sous-sol et interprétation des anomalies observées

    New Partners in Regulation of Gene Expression: The Enhancer of Trithorax and Polycomb Corto Interacts with Methylated Ribosomal Protein L12 Via Its Chromodomain

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    International audienceChromodomains are found in many regulators of chromatin structure, and most of them recognize methylated lysines on histones. Here, we investigate the role of the Drosophila melanogaster protein Corto's chromodomain. The Enhancer of Trithorax and Polycomb Corto is involved in both silencing and activation of gene expression. Over-expression of the Corto chromodomain (CortoCD) in transgenic flies shows that it is a chromatin-targeting module, critical for Corto function. Unexpectedly, mass spectrometry analysis reveals that polypeptides pulled down by CortoCD from nuclear extracts correspond to ribosomal proteins. Furthermore, real-time interaction analyses demonstrate that CortoCD binds with high affinity RPL12 tri-methylated on lysine 3. Corto and RPL12 co-localize with active epigenetic marks on polytene chromosomes, suggesting that both are involved in fine-tuning transcription of genes in open chromatin. RNA-seq based transcriptomes of wing imaginal discs over-expressing either CortoCD or RPL12 reveal that both factors deregulate large sets of common genes, which are enriched in heat-response and ribosomal protein genes, suggesting that they could be implicated in dynamic coordination of ribosome biogenesis. Chromatin immunoprecipitation experiments show that Corto and RPL12 bind hsp70 and are similarly recruited on gene body after heat shock. Hence, Corto and RPL12 could be involved together in regulation of gene transcription. We discuss whether pseudo-ribosomal complexes composed of various ribosomal proteins might participate in regulation of gene expression in connection with chromatin regulators

    Increasing species richness and genetic diversity in agriculture: results of the Wheatamix project

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    Homogenization and intensive use of inputs have provided major productivity gains in agriculture during the 20th century. However, new solutions are now needed to face the quest for greater agricultural sustainability. A better use of crop genetic diversity should be an essential leverage, as it could promote various ecosystem services, in a context of increasing environmental stochasticity caused by global change. Increasing within field diversity through the use of cultivar mixtures is a timely option, testified by with some significant “success stories” in the past, and recent bibliographic reviews. Yet, cultivar mixtures are poorly developed worldwide. In this context, the Wheatamix project studies the interest of mixing wheat genotypes to reinforce the sustainability, resilience, and multi-functionality of agriculture. Analyzing the interactions among genotypes and with the environment, Wheatamix develop new blending and breeding methods to obtain performing mixtures. Complementary experimental approaches are being deployed: i) a diversity experiment (88 large wheat plots with 1, 2, 4 or 8 varieties) to quantify the effects of wheat diversity on ecosystem services; ii) replicates of the same diversity experiment in 4 sites across France under low and high inputs, to test diversity effects under a wide range of soil and climate conditions; iii) a network of 30 farms, encompassing agro-climatic variability in the Paris basin, to compare the ecological and techno-economic performance of blends and monocultures. The first results characterize various ecosystem services provided by genetic diversity (yield stability; regulation of foliar diseases; insect pest and weed biocontrol; maintenance of soil fertility; biodiversity conservation), and raise important methodological and statistical issues, crucial when studying the causal link between bundles of functional traits and delivered groups of services. Finally, the Wheatamix project emphasizes the need of a pluri-disciplinary approach when addressing agroecological subjects, and illustrates the strong mutual benefices between agronomic and ecological sciences