Populations of the Beet Cyst Nematode Heterodera schachtii Exhibit Strong Differences in Their Life-History Traits Across Changing Thermal Conditions

It is widely accepted that climate has an essential influence on the distribution of species and that temperature is the major abiotic factor that affects their life-history traits. Species with very restricted active dispersal abilities and a wide geographical distribution are thus expected to encompass distinct populations adapted to contrasted local conditions. The beet cyst nematode Heterodera schachtii is a good biological model to study temperature adaptation in populations collected from different environments. Here, we tested the effect of temperature on H. schachtii life-history traits using seven field populations from Morocco, Spain, France, Germany, Austria, Poland and Ukraine. We tested hatching and multiplication rates of each population at different temperatures, as well as hatching rates of each population after storage at different temperatures – simulating survival conditions during the inter-cropping period. Results showed a strong temperature effect on the life-history traits explored. Temperature impact on hatching (at different temperatures and after storage at different temperatures) depended on the origin of populations, separating southern from northern ones. Surprisingly, low temperatures influenced hatching less in southern populations. However, for these populations, a storage period at low temperatures strongly reduce subsequent hatching. Conversely, nematode multiplication was not differentially affected by temperatures, as favorable conditions for the host are also favorable for the parasite. Finally, a significant correlation between the genetic diversity and the level of specialization showed that the less diverse populations were more specialized than the more diverse ones

Temporal sampling helps unravel the genetic structure of naturally occurring populations of a phytoparasitic nematode. 2. Separating the relative effects of gene flow and genetic drift

International audienceStudying wild pathogen populations in natural ecosystems offers the opportunity to better understand the evolutionary dynamics of biotic diseases in crops and to enhance pest control strategies. We used simulations and genetic markers to investigate the spatial and temporal population genetic structure of wild populations of the beet cyst nematode Heterodera schachtii on a wild host plant species, the sea beet (Beta vulgaris spp. maritima), the wild ancestor of cultivated beets. Our analysis of the variation of eight microsatellite loci across four study sites showed that (i) wild H. schachtii populations displayed fine-scaled genetic structure with no evidence of substantial levels of gene flow beyond the scale of the host plant, and comparisons with simulations indicated that (ii) genetic drift substantially affected the residual signals of isolation-by-distance processes, leading to departures from migration–drift equilibrium. In contrast to what can be suspected for (crop) field populations, this showed that wild cyst nematodes have very low dispersal capabilities and are strongly disconnected from each other. Our results provide some key elements for designing pest control strategies , such as decreasing passive dispersal events to limit the spread of virulence among field nematode populations

Δ133p53β isoform pro-invasive activity is regulated through an aggregation-dependent mechanism in cancer cells

International audienceAbstract The p53 isoform, Δ133p53β, is critical in promoting cancer. Here we report that Δ133p53β activity is regulated through an aggregation-dependent mechanism. Δ133p53β aggregates were observed in cancer cells and tumour biopsies. The Δ133p53β aggregation depends on association with interacting partners including p63 family members or the CCT chaperone complex. Depletion of the CCT complex promotes accumulation of Δ133p53β aggregates and loss of Δ133p53β dependent cancer cell invasion. In contrast, association with p63 family members recruits Δ133p53β from aggregates increasing its intracellular mobility. Our study reveals novel mechanisms of cancer progression for p53 isoforms which are regulated through sequestration in aggregates and recruitment upon association with specific partners like p63 isoforms or CCT chaperone complex, that critically influence cancer cell features like EMT, migration and invasion

The quasi-universality of nestedness in the structure of quantitative plant-parasite interactions

Understanding the relationships between host range and pathogenicity for parasites, and between the efficiency and scope of immunity for hosts are essential to implement efficient disease control strategies. In the case of plant parasites, most studies have focused on describing qualitative interactions and a variety of genetic and evolutionary models has been proposed in this context. Although plant quantitative resistance benefits from advantages in terms of durability, we presently lack models that account for quantitative interactions between plants and their parasites and the evolution of these interactions. Nestedness and modularity are important features to unravel the overall structure of host-parasite interaction matrices. Here, we analysed these two features on 32 matrices of quantitative pathogenicity trait data gathered from 15 plant-parasite pathosystems consisting of either annual or perennial plants along with fungi or oomycetes, bacteria, nematodes, insects and viruses. The performance of several nestedness and modularity algorithms was evaluated through a simulation approach, which helped interpretation of the results. We observed significant modularity in only six of the 32 matrices, with two or three modules detected. For three of these matrices, modules could be related to resistance quantitative trait loci present in the host. In contrast, we found high and significant nestedness in 30 of the 32 matrices. Nestedness was linked to other properties of plant-parasite interactions. First, pathogenicity trait values were explained in majority by a parasite strain effect and a plant accession effect, with no parasite-plant interaction term. Second, correlations between the efficiency and scope of the resistance of plant genotypes, and between the host range breadth and pathogenicity level of parasite strains were overall positive. This latter result questions the efficiency of strategies based on the deployment of several genetically-differentiated cultivars of a given crop species in the case of quantitative plant immunity

Ecologie comportementale des adultes et des larves de deux coléoptères staphylinidae, parasitoïdes de la mouche du chou

Diplôme : Dr. d'UniversiteL'apport de l'écologie comportementale est essentiel dans la compréhension des comportements mis en jeu par les parasitoïdes lors des phases de recherche et d'évaluation des hôtes. Cette approche considère que ces comportements sont optimisés par la sélection naturelle, du fait de leur forte implication dans le déterminisme de la valeur adaptative des parasitoïdes. Dans le système tritrophique, Crucifères - Delia radicum - Aleochara sp, les stratégies de sélection des sites de ponte par la femelle de A. bilineata et des hôtes par les larves parasitoïdes de 1er stade de A. bilineata et A. bipustulata ont été étudiées. La démarche analytique choisie a consisté à comparer les comportements observés chez les deux parasitoïdes étudiés, aux prédictions des modèles d'optimisation développés chez les Hyménoptères parasitoïdes. Les résultats montrent que les femelles de A. bilineata maximisent leur valeur adaptative en sélectionnant les sites de ponte fournissant les meilleures chances de succès parasitaire aux larves. Cette étude met également en évidence une forte adaptation des comportements de sélection de l'hôte par les larves de 1er stade des deux espèces, à la qualité de l'hôte, à la densité d'hôtes disponibles et à la présence ou non de larves compétitrices. L'ensemble de ces résultats montrent qu'il existe une convergence des comportements de sélection entre les Coléoptères et les Hyménoptères parasitoïdes. L'acquisition, des mêmes stratégies comportementales, indépendamment, dans deux taxons phylogénétiquement distants, suggère que ces stratégies sont les plus efficaces pour répondre aux contraintes du mode de vie parasitoïde. Ces résultats sont aussi discutés en vue de l'utilisation des deux staphylins pour lutter contre D. radicum en culture de crucifères. Aleochara bilineata s'avère être l'espèce possédant le plus grand nombre de critères favorables à son utilisation en lutte biologique. Différentes perspectives sont proposées

Déterminants de la prescription des antibiotiques en médecine générale : analyse qualitative dans la région du Centre Hospitalier Annecy Genevois

France remains one of the european countries with the highest antibiotic use. In France, 93% of all antibiotics are prescribed in the outpatient setting (essentially by general practitioners [GPs]). Most of these prescriptions is inappropriate (20-50%). The bacterial resistance is due to this antibiotic’s overuse and represents a strong public health problem.The objective of this study was to assess antibiotic prescribing’s factors in ambulatory cares among GPs.Qualitative semi structured interviews of GPs from the Hospital Center Annecy-Genevois (CHANGE) area have been conducted in order to assess the key factors of prescription and non-prescription of antibiotics. Interviews have been realised until thematic saturation (absence of new thematic during two successive interviews). The verbatims have been retranscribed and separately analyzed by two researchers. These independent analyses have been then confronted.Antibiotic prescribing’s behavior was governed by a set of several factors related to physicians, patients and the relationship between patients and physicians. It has been showed that all these factors guided the therapeutic decision. The antibiotics were considered as a special therapeutic class which could influence the relationship between the general practitioner and his patient. The antibiotic prescribing’s decision is multifactorial and complex. Multitargeted interventions are necessary to influence the GPs’ behavior about antibiotics’ prescribing.La France est un des pays européens les plus consommateurs d’antibiotiques. Cette prescription d’antibiotique s'effectue essentiellement en ambulatoire (93%) par l'intermédiaire des médecins généralistes et s'avère souvent inadaptée (20-50%). Le phénomène d’antibiorésistance est une conséquence de ce mésusage et constitue un problème de santé publique. L’objectif de cette étude était d’identifier les déterminants de la prescription d’antibiotique en médecine ambulatoire auprès des médecins généralistes. La méthodologie qualitative a été utilisée pour son approche compréhensive des facteurs de prescription ou non-prescription des antibiotiques. Ces facteurs ont été explorés par l’intermédiaire d’entretiens semi-directifs des médecins généralistes de la région du Centre Hospitalier Annecy Genevois. Le nombre d’entretiens a été fixé par la saturation des données définie dans l’étude par l’absence de nouvelle thématique lors de deux entretiens successifs. La retranscription des verbatims a été analysée indépendamment par les deux enquêteurs selon une approche inductive. Les données ont fait l’objet d’une triangulation. Des déterminants relatifs aux patients, aux médecins généralistes et à la relation médecin/patient ont été retrouvés. L’interaction de ces facteurs permettait d’orienter la décision thérapeutique du médecin généraliste vers la prescription ou non d’antibiotiques. Les antibiotiques étaient considérés comme une classe thérapeutique particulière et pilier dans la relation médecin-patient. La prescription ou non d’un antibiotique est un acte plurifactoriel et complexe. Des mesures pluridirectionnelles sont donc indispensables pour optimiser cette prescription

Aide au diagnostic : confirmer une suspicion de nématodes par l'analyse

National audienceMinuscules et à l'origine de symptômes peu spécifiques, les nématodes sont des ravageurs difficiles à mettre formellement en évidence. Pour confirmer les soupçons, le recours à une analyse en laboratoire est indispensable. Encore faut-il savoir où s'adresser et quoi envoyer. Mode d'emploi du diagnostic

La lutte biologique en culture légumière de plein champ : état des connaissances sur la mouche du chou en culture de Brassica

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Fauna associated with the cablage root fly in sequential sowings of turnips

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ECOLOGIE COMPORTEMENTALE DES ADULTES ET DES LARVES DE DEUX COLEOPTERES STAPHYLINIDAE, PARASITOIDES DE LA MOUCHE DU CHOU

RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF