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Search Results: 1 - 10 of 325549 matches for " Sébastien Carrere "
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Genomic insights into strategies used by Xanthomonas albilineans with its reduced artillery to spread within sugarcane xylem vessels
Pieretti Isabelle,Royer Monique,Barbe Valérie,Carrere Sébastien
BMC Genomics , 2012, DOI: 10.1186/1471-2164-13-658
Abstract: Background Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy compared to other species of Xanthomonas. For example, this species produces a potent DNA gyrase inhibitor called albicidin that is largely responsible for inducing disease symptoms; its habitat is limited to xylem; and the species exhibits large variability. A first manuscript on the complete genome sequence of the highly pathogenic X. albilineans strain GPE PC73 focused exclusively on distinctive genomic features shared with Xylella fastidiosa—another xylem-limited Xanthomonadaceae. The present manuscript on the same genome sequence aims to describe all other pathogenicity-related genomic features of X. albilineans, and to compare, using suppression subtractive hybridization (SSH), genomic features of two strains differing in pathogenicity. Results Comparative genomic analyses showed that most of the known pathogenicity factors from other Xanthomonas species are conserved in X. albilineans, with the notable absence of two major determinants of the “artillery” of other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis gene cluster, and the type III secretion system Hrp (hypersensitive response and pathogenicity). Genomic features specific to X. albilineans that may contribute to specific adaptation of this pathogen to sugarcane xylem vessels were also revealed. SSH experiments led to the identification of 20 genes common to three highly pathogenic strains but missing in a less pathogenic strain. These 20 genes, which include four ABC transporter genes, a methyl-accepting chemotaxis protein gene and an oxidoreductase gene, could play a key role in pathogenicity. With the exception of hypothetical proteins revealed by our comparative genomic analyses and SSH experiments, no genes potentially involved in any offensive or counter-defensive mechanism specific to X. albilineans were identified, supposing that X. albilineans has a reduced artillery compared to other pathogenic Xanthomonas species. Particular attention has therefore been given to genomic features specific to X. albilineans making it more capable of evading sugarcane surveillance systems or resisting sugarcane defense systems. Conclusions This study confirms that X. albilineans is a highly distinctive species within the genus Xanthomonas, and opens new perpectives towards a greater understanding of the pathogenicity of this destructive sugarcane pathogen.
Transcriptomic analysis of the interaction between Helianthus annuus and its obligate parasite Plasmopara halstedii shows single nucleotide polymorphisms in CRN sequences
Falah As-sadi, Sébastien Carrere, Quentin Gascuel, Thibaut Hourlier, David Rengel, Marie-Christine Le Paslier, Amandine Bordat, Marie-Claude Boniface, Dominique Brunel, Jér?me Gouzy, Laurence Godiard, Patrick Vincourt
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-498
Abstract: A 454 pyrosequencing run of two infected sunflower samples (inbred lines XRQ and PSC8 infected with race 710 of P. halstedii, which exhibit incompatible and compatible interactions, respectively) generated 113,720 and 172,107 useable reads. From these reads, 44,948 contigs and singletons have been produced. A bioinformatic portal, HP, was specifically created for in-depth analysis of these clusters. Using in silico filtering, 405 clusters were defined as being specific to oomycetes, and 172 were defined as non-specific oomycete clusters. A subset of these two categories was checked using PCR amplification, and 86% of the tested clusters were validated. Twenty putative RXLR and CRN effectors were detected using PSI-BLAST. Using corresponding sequences from four races (100, 304, 703 and 710), 22 SNPs were detected, providing new information on pathogen polymorphisms.This study identified a large number of genes that are expressed during H. annuus/P. halstedii compatible or incompatible interactions. It also reveals, for the first time, that an infection mechanism exists in P. halstedii similar to that in other oomycetes associated with the presence of putative RXLR and CRN effectors. SNPs discovered in CRN effector sequences were used to determine the genetic distances between the four races of P. halstedii. This work therefore provides valuable tools for further discoveries regarding the H. annuus/P. halstedii pathosystem.Downy mildew in sunflowers (Helianthus annuus L.) is caused by the oomycete Plasmopara halstedii (Farl.) Berlese et de Toni. Both the host plant and the pathogen species originated in North America, where co-evolution has taken place [1]. As the result of the fast evolution of the pathogen and despite considerable efforts by public research and seed companies, downy mildew remains a major risk for the crop, as new races of the pathogen are bypassing the resistance of sunflower hybrids [2], which is generally based on race-specific Pl genes [3-6]. On
The complete genome sequence of Xanthomonas albilineans provides new insights into the reductive genome evolution of the xylem-limited Xanthomonadaceae
Isabelle Pieretti, Monique Royer, Valérie Barbe, Sébastien Carrere, Ralf Koebnik, Stéphane Cociancich, Arnaud Couloux, Armelle Darrasse, Jér?me Gouzy, Marie-Agnès Jacques, Emmanuelle Lauber, Charles Manceau, Sophie Mangenot, Stéphane Poussier, Béatrice Segurens, Boris Szurek, Valérie Verdier, Matthieu Arlat, Philippe Rott
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-616
Abstract: The complete genome of X. albilineans was sequenced and annotated. X. albilineans, which is not known to be insect-vectored, also has a reduced genome and does not possess hrp genes. Phylogenetic analysis using X. albilineans genomic sequences showed that X. fastidiosa belongs to the Xanthomonas group. Order of divergence of the Xanthomonadaceae revealed that X. albilineans and X. fastidiosa experienced a convergent reductive genome evolution during their descent from the progenitor of the Xanthomonas genus. Reductive genome evolutions of the two xylem-limited Xanthomonadaceae were compared in light of their genome characteristics and those of obligate animal symbionts and pathogens.The two xylem-limited Xanthomonadaceae, during their descent from a common ancestral parent, experienced a convergent reductive genome evolution. Adaptation to the nutrient-poor xylem elements and to the cloistered environmental niche of xylem vessels probably favoured this convergent evolution. However, genome characteristics of X. albilineans differ from those of X. fastidiosa and obligate animal symbionts and pathogens, indicating that a distinctive process was responsible for the reductive genome evolution in this pathogen. The possible role in genome reduction of the unique toxin albicidin, produced by X. albilineans, is discussed.The Xanthomonadaceae are a family of Gram negative bacteria belonging to the order Xanthomonadales in the gamma subdivision of the Proteobacteria [1]. Members of this family are typically characterized as environmental organisms and occupy diverse ecological niches, such as soil and water, as well as plant tissues. Many Xanthomonadaceae, especially species from the genera Xanthomonas and Xylella, cause plant diseases and only one, Stenotrophomonas maltophilia, is known to be an opportunistic human pathogen.Complete genome sequences of several Xanthomonas species and Xylella fastidiosa strains have been determined, making those bacteria attractive models fo
Euler, Reader of Newton: Mechanics and Algebraic Analysis  [PDF]
Sébastien Maronne, Marco Panza
Advances in Historical Studies (AHS) , 2014, DOI: 10.4236/ahs.2014.31003
Abstract: We follow two of the many paths leading from Newton’s to Euler’s scientific productions, and give an account of Euler’s role in the reception of some of Newton’s ideas, as regards two major topics: mechanics and algebraic analysis. Euler contributed to a re-appropriation of Newtonian science, though transforming it in many relevant aspects. We study this re-appropriation with respect to the mentioned topics and show that it is grounded on the development of Newton’s conceptions within a new conceptual frame also influenced by Descartes’s views sand Leibniz’s formalism.
A Review of Enrofloxacin for Veterinary Use  [PDF]
Tessa Trouchon, Sébastien Lefebvre
Open Journal of Veterinary Medicine (OJVM) , 2016, DOI: 10.4236/ojvm.2016.62006
Abstract: This review outlines the current knowledge on the use of enrofloxacin in veterinary medicine from biochemical mechanisms to the use in the field conditions and even resistance and ecotoxicity. The basics of biochemistry, the mechanisms of action and resistance and pharmacokinetics are presented. Then an overview of available veterinary products, their efficacy and their toxicity against target species, human and environment is provided.
Room temperature Optical Orientation of Exciton Spin in cubic GaN/AlN quantum dots
D. Lagarde,A. Balocchi,H. Carrere,P. Renucci,T. Amand,X. Marie,S. Founta,H. Mariette
Physics , 2007, DOI: 10.1103/PhysRevB.77.041304
Abstract: The optical orientation of the exciton spin in an ensemble of self-organized cubic GaN/AlN quantum dots is studied by time-resolved photoluminescence. Under a polarized quasi-resonant excitation, the luminescence linear polarization exhibits no temporal decay, even at room temperature. This demonstrates the robustness of the exciton spin polarization in these cubic nitride nanostructures, with characteristic decay times longer than 10 ns.
Rate of Inappropriate Imaging Utilization by the Emergency Department in Community Hospitals  [PDF]
Sébastien Robert, Murray Asch, Larry Nijmeh
Open Journal of Radiology (OJRad) , 2018, DOI: 10.4236/ojrad.2018.84031
Abstract: Objective: To retrospectively analyse the use of imaging studies in the Emergency Department of community hospitals using evidence based guidelines and clinical judgement. Methods: Medical records of 661 patients who visited the Emergency Department (ED) in 2015 and underwent imaging studies were reviewed. The Canadian Association of Radiologists, American College of Radiologists and Choosing Wisely Canada guidelines were used to determine the appropriateness of imaging studies. The use of prior patient imaging, the rate at which studies were repeated and the respective impacts on patient management of the imaging studies were also examined. Results: Of the 1056 imaging studies reviewed, 228 (22%) were found to be clinical situations where no imaging study was indicated while 168 (16%) were considered a suboptimal choice of imaging study or modality. When no study was recommended, a positive impact on the diagnosis was noted in 105 (46%) cases and on patient management 83 (36%) times. Notably, 219 (21%) patients had a relevant examination performed in the last 30 days, and 147 (14%) reports noted that the results of the prior study also concurred with the imaging study evaluated. Conclusion: In this study, 228 (22%) radiographs and CT studies, excluding MVC related imaging and extremity imaging, were not indicated based on appropriateness criteria and consequently had a limited impact on patient management. This supports the need for increased clinical decision support for ED physicians, regional health information exchanges and consideration of Computerized Physician Order Entry in the ED with embedded appropriateness criteria at the point of ordering.
Three-Points Modulator Based on DPLL for Wideband Polar Modulation  [PDF]
Julien Kieffer, Sébastien Rieubon, Marc Houdebine, Sébastien Dedieu, Emil Novakov
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2027
Abstract: We present a nonlinear event-driven model of a Digital PLL used in the context of a polar modulation. This modeling has shown that the estimation method of the TDC gain has a big impact on the EVM for wideband modulation and a solution has been proposed which consists to add the modulation on the gain after calibration of the gain offset. This transforms the classical two-points modulator into a three-points modulator. This implementation has been validated for WCDMA standard.
Influence of Multiscale Roughness Patterns in Cavitated Flows: Applications to Journal Bearings
Sébastien Martin
Mathematical Problems in Engineering , 2008, DOI: 10.1155/2008/439319
Abstract: This paper deals with the coupling of two major problems in lubrication theory: cavitation phenomena and roughness of the surfaces in relative motion. Cavitation is defined as the rupture of the continuous film due to the formation of air bubbles, leading to the presence of a liquid-gas mixture. For this, the Elrod-Adams model (which is a pressure-saturation model) is classically used to describe the behavior of a cavitated thin film flow. In addition, in practical situations, the surfaces of the devices are rough, due to manufacturing processes which induce defaults. Thus, we study the behavior of the solution, when highly oscillating roughness effects on the rigid surfaces occur. In particular, we deal with the reiterated homogenization of this Elrod-Adams problem, using periodic unfolding methods. A numerical simulation illustrates the behavior of the solution. Although the pressure tends to a smooth one, the saturation oscillations are not damped. This does not prevent us from defining an equivalent homogenized saturation and highlights the anisotropic effects on the saturation function in cavitated areas.
Interspecific Hybridization as a Tool to Understand Vocal Divergence: The Example of Crowing in Quail (Genus Coturnix)
Sébastien Derégnaucourt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009451
Abstract: Understanding the mechanisms that lead organisms to be separated into distinct species remains a challenge in evolutionary biology. Interspecific hybridization, which results from incomplete reproductive isolation, is a useful tool to investigate such mechanisms. In birds, interspecific hybridization is relatively frequent, despite the fact that closed species exhibit morphological and behavioural differences. Evolution of behaviour is difficult to investigate on a large timescale since it does not ‘fossilize’. Here I propose that calls of hybrid non-songbirds that develop without the influence of learning may help in understanding the gradual process that leads to vocal divergence during speciation. I recorded crows produced by the European quail (Coturnix c. coturnix), the domestic Japanese quail (Coturnix c. japonica) and their hybrids (F1, F2 and backcrosses). Most crowing patterns were intermediate to those of the parental species; some were similar to one or the other parental species, or not present in either parental species. I also observed vocal changes in hybrid crows during the breeding season and from one year to the other. This vocal variability resembles those observed during the ontogeny of the crow in quails. It is likely that similar mechanisms involved in vocal changes during ontogeny might have driven vocal divergence in the species of Palearctic quails. I suggest that hybrid crows might have resembled those produced by intermediary forms of quails during speciation.
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