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Root-knot nematodes (genus Meloidogyne) exhibit a diversity of reproductive modes ranging from obligatory sexual to fully asexual reproduction. Intriguingly, the most widespread and devastating species to global agriculture are those that reproduce asexually, without meiosis. To disentangle this surprising parasitic success despite the absence of sex and genetic exchanges, we have sequenced and assembled the genomes of three obligatory ameiotic and asexual Meloidogyne. We have compared them to those of relatives able to perform meiosis and sexual reproduction. We show that the genomes of ameiotic asexual Meloidogyne are large, polyploid and made of duplicated regions with a high within-species average nucleotide divergence of ~8%. Phylogenomic analysis of the genes present in these duplicated regions suggests that they originated from multiple hybridization events and are thus homoeologs. We found that up to 22% of homoeologous gene pairs were under positive selection and these genes covered a wide spectrum of predicted functional categories. To biologically assess functional divergence, we compared expression patterns of homoeologous gene pairs across developmental life stages using an RNAseq approach in the most economically important asexually-reproducing nematode. We showed that >60% of homoeologous gene pairs display diverged expression patterns. These results suggest a substantial functional impact of the genome structure. Contrasting with high within-species nuclear genome divergence, mitochondrial genome divergence between the three ameiotic asexuals was very low, signifying that these putative hybrids share a recent common maternal ancestor. Transposable elements (TE) cover a ~1.7 times higher proportion of the genomes of the ameiotic asexual Meloidogyne compared to the sexual relative and might also participate in their plasticity. The intriguing parasitic success of asexually-reproducing Meloidogyne species could be partly explained by their TE-rich composite genomes, resulting from allopolyploidization events, and promoting plasticity and functional divergence between gene copies in the absence of sex and meiosis.

Root-knot nematodes (RKN), from the Meloidogyne genus, have a worldwide distribution and cause severe economic damage to many life-sustaining crops. Because of their lack of specificity and danger to the environment, most chemical nematicides have been banned from use. Thus, there is a great need for new and safe compounds to control RKN. Such research involves identifying beforehand the nematode proteins essential to the invasion. Since G protein-coupled receptors GPCRs are the target of a large number of drugs, we have focused our research on the identification of putative nematode GPCRs such as those capable of controlling the movement of the parasite towards (or within) its host. A datamining procedure applied to the genome of Meloidogyne incognita allowed us to identify a GPCR, belonging to the neuropeptide GPCR family that can serve as a target to carry out a virtual screening campaign. We reconstructed a 3D model of this receptor by homology modeling and validated it through extensive molecular dynamics simulations. This model was used for large scale molecular dockings which produced a filtered limited set of putative antagonists for this GPCR. Preliminary experiments using these selected molecules allowed the identification of an active compound, namely C260-2124, from the ChemDiv provider, which can serve as a starting point for further investigations.

The objective of this study is to evaluate which production information can be deduced from a 4D seismic survey during the Steam-Assisted Gravity Drainage (SAGD) recovery process. Superimposed on reservoir heterogeneities of geological origin, many factors interact during thermal production of heavy oil and bitumen reservoirs, which complicate the interpretation of 4D seismic data: changes in oil viscosity, in fluid saturations, in pore pressure and so on. This study is based on the real Hangingstone field case of the McMurray formation in the Athabasca region (Canada). In previous works, an initial static model (geology, petroacoustic and geomechanical) has been constructed and a thermal production of heavy oil with two coupled fluid-flow and geomechanical models has been simulated. Seismic parameters (density, compression velocity and shear velocity) of the saturated rocks have then been computed from mechanical and reservoir parameters at several stages of the production. A repeated acquisition survey is modelled at different stages of SAGD production. This is performed using a 3D seismic modelling approach. To focus on the reflections generated within the reservoir zone, a target-oriented modelling is chosen. It is based on the ray+Born approach which permits to compute the P-wave elastic response by correctly handling the seismic amplitudes as a function of source-receiver offset. Real incoherent noise is added to the zero-phase synthetic data to produce a more realistic result. The noise-free and the noisy synthetic data are processed to get stacked and time migrated images. A simple processing workflow leads to image the steam chamber development, in particular its V-shape in radial section, and to observe time-lapse in the reservoir zone. An interpretation work is then carried out. Some seismic attributes like RMS values of amplitude changes between stages, energy, time differences of reservoir bottom between stages, etc. are computed from the synthetic (noise-free and noisy) seismic data. Some of these attributes prove to be robust to the noise and to show some production effect. Possible trends between these attributes and the modelled reservoir/geomechanical properties (lithofacies, pressure, temperature, steam saturation, etc.) are also evaluated. Finally, geobodies are extracted from the seismic attributes. L’objectif de cette étude est d’évaluer quelle information de production peut être déduite d’une campagne sismique 4D durant le procédé de récupération par injection de vapeur SAGD (Steam- Assisted Gravity Drainage). En plus des hétérogénéités réservoir d’origine géologique, de nombreux facteurs interagissent pendant la production thermique d’huile lourde et de bitume, ce qui complique l’interprétation des données sismiques 4D : variation de la viscosité de l’huile, des saturations en fluide, de la pression de pore, etc. Cette étude est basée sur le champ pétrolier Hangingstone de la formation McMurray en Athabasca (Canada). Dans des travaux antérieurs, un modèle statique initial (géologique, pétroacoustique et géomécanique) avait été construit. Puis la production thermique d’huile lourde avait été simulée en mettant en oeuvre le couplage d’un modèle d’écoulement de réservoir et d’un modèle géomécanique. Les paramètres sismiques des roches saturées (densité, vitesses de compression et de cisaillement) avaient alors été calculés à plusieurs étapes de la production à partir des paramètres mécaniques et de réservoir. À partir de ces résultats, une acquisition sismique est simulée à quatre états de production SAGD. Comme on s’intéresse aux réflexions sismiques en ondes de compression générées dans le réservoir, une modélisation sismique orientée cible est choisie. Cette modélisation est basée sur une approche ray+Born et permet de calculer la réponse sismique en estimant correctement les amplitudes sismiques en fonction de l’offset (distance source-récepteur). Pour obtenir des données plus réalistes, du bruit réel incohérent est ajouté aux données sismiques synthétiques. Les jeux de données synthétiques non bruitées et bruitées sont ensuite traités afin d’obtenir des images sismiques temps sommées et migrées. Une séquence simple de traitement sismique permet d’imager le développement de la chambre de vapeur, en particulier sa forme en V dans le plan perpendiculaire aux drains horizontaux, et d’observer des différences de temps de trajet dans la zone réservoir. Un travail d’interprétation est alors mené sur ces données sismiques synthétiques à différents états de production. Plusieurs attributs sismiques, comme les valeurs RMS des variations d’amplitude entre états, les variations de temps de trajet à la base du réservoir entre états, ou l’énergie des images sismiques à chaque état, sont calculés sur les données synthétiques non bruitées et bruitées. Quelques attributs sismiques apparaissent robustes au bruit et impactés par la production. Les relations entre ces attributs sismiques et les propriétés réservoir/géomécaniques (lithofaciès, pression, température, saturation en vapeur d’eau, etc.) sont aussi évaluées. Enfin, concernant l’interprétation sismique, des corps réservoir connectés (geobodies) sont extraits des attributs sismiques.

The origin of plant parasitism within the phylum Nematoda is intriguing. The ability to parasitize plants has originated independently at least three times during nematode evolution and, as more molecular data has emerged, it has become clear that multiple instances of horizontal gene transfer (HGT) from bacteria and fungi have played a crucial role in the nematode's adaptation to this new lifestyle. The first reported HGT cases in plant-parasitic nematodes were genes encoding plant cell wall–degrading enzymes. Other putative examples of HGT were subsequently described, including genes that may be involved in the modulation of the plant's defense system, the establishment of a nematode feeding site, and the synthesis or processing of nutrients. Although, in many cases, it is difficult to pinpoint the donor organism, candidate donors are usually soil dwelling and are either plant-pathogenic or plant-associated microorganisms, hence occupying the same ecological niche as the nematodes. The exact mechanisms of transfer are unknown, although close contacts with donor microorganisms, such as symbiotic or trophic interactions, are a possibility. The widespread occurrence of horizontally transferred genes in evolutionarily independent plant-parasitic nematode lineages suggests that HGT may be a prerequisite for successful plant parasitism in nematodes.

Reports on survey about suicide among 15- to 24-year-olds (N=15,555) in 34 of the wealthiest nations. Finland led in total and firearm-related suicides. An association was found between divorce rates and youth suicide rates, firearm-related suicide, and suicide rates among young males. An association was found between firearm availability and firearm-related suicide rates among young males. (Author/JDM)

En 1966, la Organización Mundial de la Salud declaró la violencia como uno de los principales problemas de salud pública. Para dar seguimiento a dicha resolución, el 3 de octubre de este año, la OMS publicó el primer Informe mundial sobre la violencia y la salud, el cual analiza los diferentes tipos de violencia, incluidos el maltrato y abandono de menores, la violencia entre los jóvenes, la violencia contra la pareja, la violencia sexual, el maltrato a ancianos, la violencia autoinfligida y la violencia colectiva. Para todos estos tipos de violencia, el informe explora la magnitud de sus efectos en la salud y en la sociedad, los factores de riesgo y protección y los esfuerzos de prevención que se han desplegado. El lanzamiento del informe dará inicio a una Campaña Global de Prevención de la Violencia que durante un año se centrará en la aplicación de sus recomendaciones. Este artículo resume algunos de los puntos más importantes del informe mundial.