Genome-wide examination of the transcriptional response to ecdysteroids 20-hydroxyecdysone and ponasterone A in Drosophila melanogaster

<p>Abstract</p> <p>Background</p> <p>The 20-hydroxyecdysone (20E) hierarchy of gene activation serves as an attractive model system for studying the mode of steroid hormone regulated gene expression and development. Many structural analogs of 20E exist in nature and among them the plant-derived ponasterone A (PoA) is the most potent. PoA has a higher affinity for the 20E nuclear receptor, composed of the ecysone receptor (EcR) and Ultraspiracle proteins, than 20E and a comparison of the genes regulated by these hormones has not been performed. Furthermore, in <it>Drosophila </it>different cell types elicit different morphological responses to 20E yet the cell type specificity of the 20E transcriptional response has not been examined on a genome-wide scale. We aim to characterize the transcriptional response to 20E and PoA in <it>Drosophila </it>Kc cells and to 20E in salivary glands and provide a robust comparison of genes involved in each response.</p> <p>Results</p> <p>Our genome-wide microarray analysis of Kc167 cells treated with 20E or PoA revealed that far more genes are regulated by PoA than by 20E (256 vs 148 respectively) and that there is very little overlap between the transcriptional responses to each hormone. Interestingly, genes induced by 20E relative to PoA are enriched in functions related to development. We also find that many genes regulated by 20E in Kc167 cells are not regulated by 20E in salivary glands of wandering 3^rdinstar larvae and we show that 20E-induced levels of <it>EcR </it>isoforms <it>EcR-RA, ER-RC</it>, and <it>EcR-RD/E </it>differ between Kc cells and salivary glands suggesting a possible cause for the observed differences in 20E-regulated gene transcription between the two cell types.</p> <p>Conclusions</p> <p>We report significant differences in the transcriptional responses of 20E and PoA, two steroid hormones that differ by only a single hydroxyl group. We also provide evidence that suggests that PoA induced death of non-adapted insects may be related to PoA regulating different set of genes when compared to 20E. In addition, we reveal large differences between Kc cells and salivary glands with regard to their genome-wide transcriptional response to 20E and show that the level of induction of certain EcR isoforms differ between Kc cells and salivary glands. We hypothesize that the differences in the transcriptional response may in part be due to differences in the EcR isoforms present in different cell types.</p

Evolution des connaissances du bassin Anglo-Parisien - Apports de la géologie marine : Exemple du Mésozoïque et des géométries sédimentaires de la craie du pays de Caux

International audienceLe " Bassin de Paris " fait partie intégrante du bassin sédimentaire intracratonique Anglo-Parisien, qui couvre une majeure partie du Nord de la France et du Sud-Est de l'Angleterre. A plusieurs reprises, les phases de déformation tectonique affectent l'évolution du bassin en modifiant la sédimentation, la répartition des aires de subsidence, et l'orientation des paléogéographies, notamment sur sa bordure ouest à la transition Jurassique-Crétacé et lors de l'inversion en Manche au Cénozoïque. Cette évolution du remplissage sédimentaire et de la tectonique de cette zone reste encore peu détaillée en raison d'un manque de données de subsurface (puits, sismique), généralement localisées au centre du Bassin de Paris. De 2007 à 2009, les missions d'acquisition sismique (BaiSeine07, SeineHR08 et SeineTHR08) et de prélèvements au carottier à roche (Carobseine09) ont été effectuées en baie de Seine dans le cadre d'une collaboration Université de Caen-Basse Normandie / BRGM. La qualité et la densité des données acquises a permis de détailler le substratum mésozoïque, principalement jurassique, de part et d'autre de la Paléo-Seine plio-quaternaire, et de proposer une cartographie géologique révisée de baie de Seine (thèse de M. Benabdellouahed, 2011). Quelques profils acquis au large du Pays de Caux permettent d'étendre les études aux séries du Crétacé à l'est. L'interprétation de ces profils, couplés aux données bathymétriques (SHOM), topographiques Lidar et photographiques (IGN), et de sondage en mer (BRGM), ont permis (i) d'effectuer les corrélations terre-mer fines, (ii) d'établir un atlas sismique des formations crétacées, (iii) d'imager les structures et les géométries principales du remplissage cénozoïque, et (iv) d'étendre la cartographie géologique de baie de Seine vers le nord et l'est (Paquet et al., en prep.). Un exemple d'apport de connaissance est l'imagerie fine des géométries sédimentaires en ondulation de la craie, visibles sur les falaises et le platier entre Etretat et Fécamp. Ces géométries trouvent leur origine dans des courants marins affectant le fond. Une meilleure connaissance de leurs dimensions, orientation et extension géographique fournira des éléments pour mieux comprendre la paléogéographie de la zone et son évolution au Crétacé supérieur. La campagne MERCAUX d'acquisition sismique " sparker " très haute résolution (aout-septembre 2013) s'intègre dans cette logique d'amélioration des connaissances de la bordure ouest du Bassin anglo-parisien, et de son évolution géologique

Evolution des connaissances du bassin Anglo-Parisien - Apports de la géologie marine : Exemple du Mésozoïque et des géométries sédimentaires de la craie du pays de Caux

International audienceLe " Bassin de Paris " fait partie intégrante du bassin sédimentaire intracratonique Anglo-Parisien, qui couvre une majeure partie du Nord de la France et du Sud-Est de l'Angleterre. A plusieurs reprises, les phases de déformation tectonique affectent l'évolution du bassin en modifiant la sédimentation, la répartition des aires de subsidence, et l'orientation des paléogéographies, notamment sur sa bordure ouest à la transition Jurassique-Crétacé et lors de l'inversion en Manche au Cénozoïque. Cette évolution du remplissage sédimentaire et de la tectonique de cette zone reste encore peu détaillée en raison d'un manque de données de subsurface (puits, sismique), généralement localisées au centre du Bassin de Paris. De 2007 à 2009, les missions d'acquisition sismique (BaiSeine07, SeineHR08 et SeineTHR08) et de prélèvements au carottier à roche (Carobseine09) ont été effectuées en baie de Seine dans le cadre d'une collaboration Université de Caen-Basse Normandie / BRGM. La qualité et la densité des données acquises a permis de détailler le substratum mésozoïque, principalement jurassique, de part et d'autre de la Paléo-Seine plio-quaternaire, et de proposer une cartographie géologique révisée de baie de Seine (thèse de M. Benabdellouahed, 2011). Quelques profils acquis au large du Pays de Caux permettent d'étendre les études aux séries du Crétacé à l'est. L'interprétation de ces profils, couplés aux données bathymétriques (SHOM), topographiques Lidar et photographiques (IGN), et de sondage en mer (BRGM), ont permis (i) d'effectuer les corrélations terre-mer fines, (ii) d'établir un atlas sismique des formations crétacées, (iii) d'imager les structures et les géométries principales du remplissage cénozoïque, et (iv) d'étendre la cartographie géologique de baie de Seine vers le nord et l'est (Paquet et al., en prep.). Un exemple d'apport de connaissance est l'imagerie fine des géométries sédimentaires en ondulation de la craie, visibles sur les falaises et le platier entre Etretat et Fécamp. Ces géométries trouvent leur origine dans des courants marins affectant le fond. Une meilleure connaissance de leurs dimensions, orientation et extension géographique fournira des éléments pour mieux comprendre la paléogéographie de la zone et son évolution au Crétacé supérieur. La campagne MERCAUX d'acquisition sismique " sparker " très haute résolution (aout-septembre 2013) s'intègre dans cette logique d'amélioration des connaissances de la bordure ouest du Bassin anglo-parisien, et de son évolution géologique

Deep-water dunes on drowned isolated carbonate terraces (Mozambique Channel, south-west Indian Ocean)

International audienceSubaqueous sand dunes are common bedforms on continental shelves dominated by tidal and geostrophic currents. However, much less is known about sand dunes in deep-marine settings that are affected by strong bottom currents. In this study, dune fields were identified on drowned isolated carbonate platforms in the Mozambique Channel (south-west Indian Ocean). The acquired data include multibeam bathymetry, multi-channel high-resolution seismic reflection data, sea floor imagery, a sediment sample and current measurements from a moored current meter and hull-mounted acoustic Doppler current profiler. The dunes are located at water depths ranging from 200 to 600 m on the slope terraces of a modern atoll (Bassas da India Atoll) and within small depressions formed during tectonic deformation of drowned carbonate platforms (Sakalaves Seamount and Jaguar Bank). Dunes are composed of bioclastic medium size sand, and are large to very large, with wavelengths of 40 to 350 m and heights of 0·9 to 9·0 m. Dune migration seems to be unidirectional in each dune field, suggesting a continuous import and export of bioclastic sand, with little sand being recycled. Oceanic currents are very intense in the Mozambique Channel and may be able to erode submerged carbonates, generating carbonate sand at great depths. A mooring located at 463 m water depth on the Hall Bank (30 km west of the Jaguar Bank) showed vigorous bottom currents, with mean speeds of 14 cm sec−1 and maximum speeds of 57 cm sec−1, compatible with sand dune formation. The intensity of currents is highly variable and is related to tidal processes (high-frequency variability) and to anticyclonic eddies near the seamounts (low-frequency variability). This study contributes to a better understanding of the formation of dunes in deep-marine settings and provides valuable information about carbonate preservation after drowning, and the impact of bottom currents on sediment distribution and sea floor morphology. © 2018 The Authors. Sedimentology © 2018 International Association of Sedimentologist

First characterization of the volcanism in the southern Mozambique Channel: Geomorphological and structural analyses

International audienceThe southern part of the Mozambique Channel is characterized by a cluster of isolated seamounts, including the Bassas da India atoll and Europa Island, ranging in latitude from 20°S to 22°S and from 38° to 40° in longitude, and located at the Rovuma-Lwandle plate boundary. Only Cenozoic carbonate platforms have previously been studied in this region, with very little work done on the volcanic history. We confirm here the volcanic nature of the basement of the Bassa da India/Europa complex by providing important constraints on the setting of this hitherto poorly understood volcanism.Recent bathymetric surveys and dredging operations allowed us to map and date these seamounts, comprising, from west to east, the Hall Bank, the Jaguar Bank, Bassas da India, Ptolemee, and Europa. In addition, we discovered, to the south of Bassas da India, two large new polygenetic volcanic edifices, Pamela Seamount 1 (PS1) and Pamela Seamount 2 (PS2), showing heights and diameters of up to 900 m and 13 km, respectively. Mapping and statistical analysis carried out revealed that the volcanic structures of the Bassas da India/Europa complex are organized along two main alignments with different stages of development: (i) a NE-SW volcanic alignment characterized by volcanic ridges up to 700 m in height, comprising small individual volcanic cones; and (ii) a NW-SE volcanic alignment in which many large and well-developed individual volcanic cones can be found. From this distribution of the volcanism, we suggest that the large volcanic edifices of the Bassas da India/Europa complex were fed by long-lived magma systems, repeatedly supplied from deep magma reservoirs through a significant network of dykes and faults, with lateral injections of magma guided by a dense network of faults allowing magma to reach the surface along rift-zones. 40Ar/39Ar dating confirms that the volcanism covers a period from the Oligo-Miocene to the Pleistocene, and probably extends to the present day. The two volcanic alignments are also consistent with the tectonic features already recognized for the region and are spatially superimposed by active seismicity. Magma ascent is strongly controlled by large pre-existing crustal structures

Impact of tectonic and volcanism on the Neogene evolution of isolated carbonate platforms (SW Indian Ocean)

International audienceUnderstanding the impact of tectonic activity and volcanism on long-term (i.e. millions years) evolution ofshallow-water carbonate platforms represents a major issue for both industrial and academic perspectives. Thesouthern central Mozambique Channel is characterized by a 100 km-long volcanic ridge hosting two guyots(the Hall and Jaguar banks) and a modern atoll (Bassas da India) fringed by a large terrace. Dredge sampling, geo-physical acquisitions and submarines videos carried out during recent oceanographic cruises revealed that sub-marineflat-top seamounts correspond to karstified and drowned shallow-water carbonate platforms largelycovered by volcanic material and structured by a dense network of normal faults. Microfacies and well-constrained stratigraphic data indicate that these carbonate platforms developed in shallow-water tropical envi-ronments during Miocene times and were characterized by biological assemblages dominated by corals, largerbenthic foraminifera, red and green algae. The drowning of these isolated carbonate platforms is revealed bythe deposition of outer shelf sediments during the Early Pliocene and seems closely linked to (1) volcanic activitytypified by the establishment of wide lavaflow complexes, and (2) to extensional tectonic deformation associat-ed with high-offset normal faults dividing theflat-top seamounts into distinctive structural blocks. Explosive vol-canic activity also affected platform carbonates and was responsible for the formation of crater(s) and thedeposition of tuff layers including carbonate fragments. Shallow-water carbonate sedimentation resumed duringLate Neogene time with the colonization of topographic highs inherited from tectonic deformation and volcanicaccretion. Latest carbonate developments ultimately led to the formation of the Bassas da India modern atoll. Thegeological history of isolated carbonate platforms from the southern Mozambique Channel represents a new caseillustrating the major impact of tectonic and volcanic activity on the long-term evolution of shallow-water car-bonate platform