188 research outputs found
Optimisation de la méthode de coproscopie sur échantillons de litière pour le diagnostic collectif des infections par les coccidies chez les agneaux
La coccidiose, causée par des protozoaires intracellulaires obligatoires du genre Eimeria, est une maladie à fortes répercussions économique et sanitaire pour les élevages ovins. Actuellement, la technique de préparation utilisée pour le diagnostic collectif sur litière est le tri à la main, chronophage et peu répétable. Cette étude a donc pour objectif d’optimiser la méthode d’analyse de litière en comparant le tri à la main avec un nouveau protocole : la sédimentation. Pour ce faire, plusieurs échantillons de litière de quatre loges ont été analysés conjointement avec les deux méthodes de préparation. En parallèle, des fèces récoltées directement au rectum d’agneaux d’engraissement appartenant à ces mêmes loges ont été analysées pour déterminer si les techniques de préparation des échantillons de litière reflétaient la réelle excrétion fécale. Plusieurs facteurs ont été comparés entre les deux méthodes parmi lesquels leur mise en œuvre, leur corrélation aux fèces individuelles et la composition des échantillons. Ainsi, d’après cette étude, le tri à la main est la méthode répondant à un plus grand nombre de critères. La technique de sédimentation nécessite donc d’être améliorée afin d’optimiser le diagnostic collectif de coccidiose
Isozymes of Superoxide Dismutase in Mitochondria and Peroxisomes Isolated from Petals of Carnation ( Dianthus caryophyllus
Membrane-Associated and Soluble Lipoxygenase Isoforms in Tomato Pericarp (Characterization and Involvement in Membrane Alterations)
The Cytosolic/Nuclear HSC70 and HSP90 Molecular Chaperones Are Important for Stomatal Closure and Modulate Abscisic Acid-Dependent Physiological Responses in Arabidopsis
HINKEL kinesin, ANP MAPKKKs and MKK6/ANQ MAPKK, which phosphorylates and activates MPK4 MAPK, constitute a pathway that is required for cytokinesis in Arabidopsis thaliana
Cytokinesis is regulated to ensure the precise partitioning of cytoplasm and duplicated chromosomes to daughter cells. The NACK-PQR pathway, which includes NACK1 kinesin-like protein (KLP) and a mitogen-activated protein kinase (MAPK) cascade, plays a key role in cytokinesis in tobacco cells. Although HINKEL/AtNACK1 (HIK) KLP, ANP MAP kinase kinase kinases (MAPKKKs) and MKK6/ ANQ MAP kinase kinase (MAPKK) have been identified independently as regulators of cytokinesis in Arabidopsis thaliana, the involvement of HIK, ANPs and MKK6/ANQ in a regulatory cascade remains to be demonstrated. Here we provide details of the protein kinase pathway that controls cytokinesis in A. thaliana. Analysis of the subcellular distribution of six MAPKKs of A. thaliana that had been fused to green fluorescent protein revealed that only MKK6/ANQ protein was concentrated at the equatorial plane of the phragmoplast, at the site of localization of HIK. Expression of MKK6/ANQ in yeast cells replaced the growth-control function of the MAPKK encoded by yeast PBS2, provided that both ANP1 MAPKKK and HIK [or TETRASPORE/AtNACK2 (TES)] KLP were coexpressed, suggesting that ANP1 activates MKK6/ANQ in the presence of HIK (or TES). Coexpression of HIK and ANP3 (another member of the ANP MAPKKK family) weakly activated MKK6/ANQ but that of TES and ANP3 did not. MKK6/ANQ phosphorylated MPK4 MAPK in vitro to activate the latter kinase. Thus cytokinesis in A. thaliana is controlled by a pathway that consists of ANP MAPKKKs that can be activated by HIK and MKK6/ANQ MAPKK, with MPK4 MAPK being a probable target of MKK6/ANQ
A plastid-localized glycogen synthase kinase 3 modulates stress tolerance and carbohydrate metabolism
Glycogen synthase kinase 3 (GSK-3) was originally identified as a regulator of glycogen synthesis in mammals. Like starch in plants, glycogen is a polymer of glucose, and serves as an energy and carbon store. Starch is the main carbohydrate store in plants. Regulation of starch metabolism, in particular in response to environmental cues, is of primary importance for carbon and energy flow in plants but is still obscure. Here, we provide evidence that MsK4, a novel Medicago sativa GSK-3-like kinase, connects stress signalling with carbon metabolism. MsK4 was found to be a plastid-localized protein kinase that is associated with starch granules. High-salt stress rapidly induced the in vivo kinase activity of MsK4. Metabolic profiling of MsK4 over-expressor lines revealed changes in sugar metabolism, including increased amounts of maltose, the main degradation product of starch in leaves. Plants over-expressing MsK4 showed improved tolerance to salt stress. Moreover, under high-salinity conditions, MsK4-over-expressing plants accumulated significantly more starch and showed modified carbohydrate content compared with wild-type plants. Overall, these data indicate that MsK4 is an important regulator that adjusts carbohydrate metabolism to environmental stress
Membrane transport, sensing and signaling in plant adaptation to environmental stress
Plants are generally well adapted to a wide range of environmental conditions. Even though they have notably prospered in our planet, stressful conditions such as salinity, drought and cold or heat, which are increasingly being observed worldwide in the context of the ongoing climate changes, limit their growth and productivity. Behind the remarkable ability of plants to cope with these stresses and still thrive, sophisticated and efficient mechanisms to re-establish and maintain ion and cellular homeostasis are involved. Among the plant arsenal to keep homeostasis are efficient stress sensing and signaling mechanisms, plant cell detoxification systems, compatible solute and osmoprotectant accumulation and a vital rearrangement of solute transport and compartmentation. The key role of solute transport systems and signaling proteins in cellular homeostasis is addressed in the present work. The full understanding of the plant cell complex defense mechanisms under stress may allow for the engineering of more tolerant plants or the optimization of cultivation practices to improve yield and productivity, which is crucial in the present time as food resources are progressively scarce.This work was supported by the Portuguese Foundation for Science and Technology (FCT)
(research project ref. PTDC/AGR-ALI/100636/2008; to A. Conde, grant ref.
SFRH/BD/47699/2008)
Coevolving MAPK and PID phosphosites indicate an ancient environmental control of PIN auxin transporters in land plants
Elaboration et caractérisation de composites à matrice SiC et à interphase séquencée C/SiC
Interphases composed of alternating layers of carbon and SiC, aimed at improving the mechanical properties of SiC/SiC composites, have been developed by CVI. The analysis of the structure of the layers and then of the cracks in transmission electron microscopy makes it possible to better understand the mechanisms of cracking within a sequenced interphase. The mechanical behavior was characterized by tensile tests, according to certain interfacial properties (#0, l#s, #s,. . .). The mechanical properties were then examined by the concept of curve r. An approach linking the energy relaxation rate g to the size of the process zone at the bottom of the notch is proposed. G, determined using an equivalent system of two specimens and free of process zone, is directly expressed as a function of the complacency of the damaged material.Des interphases composées de couches alternées de carbone et de SiC, visant a améliorer les propriétés mécaniques des composites SiC/SiC, ont été élaborées par CVI. L'analyse de la structure des couches puis des fissures en microscopie électronique en transmission permet de mieux comprendre les mécanismes de fissuration au sein d'une interphase séquencée. Le comportement mécanique a été caractérisé grâce à des essais de traction, en fonction de certaines propriétés interfaciales (#0, l#s, #s,. . . ). Les propriétés mécaniques ont ensuite été examinées par le concept de courbe r. Une approche reliant le taux de relaxation d'énergie g à la taille de la process zone en fond d'entaille est proposée. G, déterminé en utilisant un système équivalent de deux éprouvettes et exemptes de process zone, est directement exprimé en fonction de la complaisance du matériau endommagé
Origine de la pathogénicité des lagovirus : avancées sur la diversité génétique virale et le développement d’un système de génétique inverse
Lagoviruses infect leporidae (rabbits and hares). Pathogenic lagoviruses such as Rabbit haemorrhagic disease virus (RHDV) and European Brown Hare Syndrome virus (EBHSV) often cause fatal viral hepatitis with serious economic and ecological consequences. Non-pathogenic lagoviruses such as European Rabbit Caliciviruses 1 and 2 (RCV-E1 and RCV-E2) and Hare Caliciviruses (HaCV) cause no disease in rabbits and hares, respectively. The emergence of a new pathogenic lagovirus in 2010, named RHDV2, infecting both rabbits and hares, led us to question the origin of lagoviruses pathogenicity. The studied hypothesis is the evolution from non-pathogenic to pathogenic strains. For this purpose, the genetic diversity of non-pathogenic lagoviruses, little known in hares, was studied in this species. Eleven new gene sequences encoding the capsid protein and the first complete genome sequence of a HaCV virus have been obtained. These data showed the high genetic diversity of HaCVs and revealed their circulation long before the first detection of EBHSV in 1980. However, no evolutionary link was found between HaCV and EBHSV. New sequences of complete genomes or coding regions of RCV-E1 and RHDV2 were also characterized. Genetic analyses suggested that a recombination event between an RCV-E1 virus and an unknown virus was at the origin of the emergence of RHDV2. In the second part of the thesis, we attempted to develop a new reverse genetics (RG) system for the RHDV in order to study the molecular basis of the pathogenicity of lagoviruses. The in vivo genotype and phenotype of a reference RHDV strain were characterized and then in vitro and in vivo regeneration assays of this strain in RG were performed to validate the system under development. The results showed that the system was able to produce viral RNA and capsid protein in vitro. In vivo assay to regenerate the virus did not result in the infection of rabbits. However, the majority of the animals seroconverted. These results did not lead to the conclusion that the RG system was able to produce infectious viral particles and points for improvement are proposed.Les lagovirus infectent les léporidés (lapins et lièvres). Les lagovirus pathogènes tels que le Rabbit haemorragic disease virus (RHDV) et l’European Brown Hare Syndrome virus (EBHSV) provoquent des hépatites virales souvent mortelles ayant de graves conséquences économiques et écologiques. Les lagovirus non-pathogènes tels que les European Rabbit Calicivirus 1 et 2 (RCV-E1 et RCV-E2) et les Hare Calicivirus (HaCV) ne provoquent aucune maladie chez les lapins et les lièvres, respectivement. L’émergence d’un nouveau lagovirus pathogène en 2010, nommé RHDV2, capable d’infecter à la fois les lapins et les lièvres, nous a poussé à nous interroger sur l’origine de la pathogénicité chez les lagovirus. L’hypothèse étudiée est l’évolution de souches non-pathogènes vers des souches pathogènes. Pour cela, la diversité génétique des lagovirus non-pathogènes, peu connue chez le lièvre, a été étudiée chez cette espèce. Onze nouvelles séquences de gène codant la protéine de capside et la première séquence du génome complet d’un virus HaCV ont été obtenues. Ces données ont montré la grande diversité génétique des HaCV et leur circulation bien avant la première détection des EBHSV en 1980. Toutefois, aucun lien évolutif n’a été trouvé avec les EBHSV. De nouvelles séquences de génomes complets ou de régions codantes de RCV-E1 et de RHDV2 ont aussi été caractérisées. Les analyses génétiques ont suggéré qu’un évènement de recombinaison entre un virus RCV-E1 et un virus inconnu était à l’origine de l’émergence des RHDV2. Dans la seconde partie de la thèse, nous avons tenté de développer un nouveau système de génétique inverse (GI) pour le RHDV afin d’étudier les bases moléculaires du pouvoir pathogène. Le génotype et le phénotype in vivo d’une souche RHDV de référence ont été caractérisés, puis des essais de régénération de cette souche en GI ont été effectués in vitro et in vivo pour valider le système en cours de développement. Les résultats obtenus ont montré que le système était capable de produire de l’ARN viral et la protéine de capside in vitro. Les essais in vivo visant à régénérer le virus n’ont pas permis l’infection de lapins. Cependant, la majorité des animaux ont séroconverti. Ces résultats n’ont pas permis de conclure que le système de GI était capable de produire des particules virales infectieuses et des points d’amélioration sont proposés
- …