HAL-UNICE
Not a member yet
30584 research outputs found
Sort by
From structure to function - a family portrait of plant subtilases
No full textSubtilases (SBTs) are serine peptidases that are found in all three domains of life. As compared with homologs in other Eucarya, plant SBTs are more closely related to archaeal and bacterial SBTs, with which they share many biochemical and structural features. However, in the course of evolution, functional diversification led to the acquisition of novel, plant-specific functions, resulting in the present-day complexity of the plant SBT family. SBTs are much more numerous in plants than in any other organism, and include enzymes involved in general proteolysis as well as highly specific processing proteases. Most SBTs are targeted to the cell wall, where they contribute to the control of growth and development by regulating the properties of the cell wall and the activity of extracellular signaling molecules. Plant SBTs affect all stages of the life cycle as they contribute to embryogenesis, seed development and germination, cuticle formation and epidermal patterning, vascular development, programmed cell death, organ abscission, senescence, and plant responses to their biotic and abiotic environments. In this article we provide a comprehensive picture of SBT structure and function in plants
Genome-wide association studies in plant pathosystems: toward an ecological genomics approach.
No full textThe emergence and re-emergence of plant pathogenic microorganisms are processes that imply perturbations in both host and pathogen ecological niches. Global change is largely assumed to drive the emergence of new etiological agents by altering the equilibrium of the ecological habitats which in turn places hosts more in contact with pathogen reservoirs. In this context, the number of epidemics is expected to increase dramatically in the next coming decades both in wild and crop plants. Under these considerations, the identification of the genetic variants underlying natural variation of resistance is a pre-requisite to estimate the adaptive potential of wild plant populations and to develop new breeding resistant cultivars. On the other hand, the prediction of pathogen's genetic determinants underlying disease emergence can help to identify plant resistance alleles. In the genomic era, whole genome sequencing combined with the development of statistical methods led to the emergence of Genome Wide Association (GWA) mapping, a powerful tool for detecting genomic regions associated with natural variation of disease resistance in both wild and cultivated plants. However, GWA mapping has been less employed for the detection of genetic variants associated with pathogenicity in microbes. Here, we reviewed GWA studies performed either in plants or in pathogenic microorganisms (bacteria, fungi and oomycetes). In addition, we highlighted the benefits and caveats of the emerging joint GWA mapping approach that allows for the simultaneous identification of genes interacting between genomes of both partners. Finally, based on co-evolutionary processes in wild populations, we highlighted a phenotyping-free joint GWA mapping approach as a promising tool for describing the molecular landscape underlying plant - microbe interactions
Exopolysaccharide Quantification for the Plant Pathogen Ralstonia solanacearum
No full textSoluble exopolysaccharide is a major virulence factor produced by the plant pathogen Ralstonia solanacearum. Its massive production during plant infection is associated with the arrest of water flow in xylem vessels leading eventually to plant death. The composition of this heavy macromolecule includes mainly N-acetylgalactosamine. Here we describe a colorimetric method for quantitative determination of the soluble exopolysaccharide present in culture supernatant of R. solanacearum
Genome sequencing and transcriptome analysis of Trichoderma reesei QM9978 strain reveals a distal chromosome translocation to be responsible for loss of vib1 expression and loss of cellulase induction
No full textInternational audienc
Asymmetric synthesis of glutamate derivatives
No full textInternational audienceAnalogs of glutamic acid were synthesized through the asymmetric Michael reaction using chiral acyclicβ-enaminoesters and various Michael acceptors. The influence of the alkoxy group of the enaminoesters andalso the nature of the olefins in the presence or not of zinc chloride on yield and enantioselectivity areexplored
In Vitro and in Vivo Evaluation of Fully Substituted (5-(3-Ethoxy-3-oxopropynyl)-4-(ethoxycarbonyl)-1,2,3-triazolyl-glycosides as Original Nucleoside Analogues to Circumvent Resistance in Myeloid Malignancies
No full textInternational audienceA series of nucleoside analogues bearing a 1,4,5-trisubstituted-1,2,3-triazole aglycone was synthesized using a straightforward click/electrophilic addition or click/oxidative coupling tandem procedures. SAR analysis, using cell culture assays, led to the discovery of a series of compounds belonging to the 5-alkynyl-1,2,3-triazole family that exhibits potent antileukemic effects on several hematologic malignancies including chronic myeloid leukemia (CML) and myelodysplastic syndromes (MDS) either sensitive or resistant to their respective therapy. Compound 4a also proved efficient in vivo on mice xenografted with SKM1-R MDS cell line. Additionally, some insights in its mode of action revealed that this compound induced cell death by caspase and autophagy induction
Retournement, flexion, étirement : particules dans les écoulements laminaires et chaotiques
No full textParticles, when subjected into a flow, may display preferred orientations and a variety of deformations depending on their geometry and elasticity and the flow velocity field. Flows can conversely be modified when the particle stresses are sufficiently large. This thesis presents theoretical and numerical results on this two-way relationship between particles and flows in two parts. Part I starts with a stability analysis and numerical simulations that show a simple semiflexible Brownian particle in an extensional flow undergo tumbling, a phenomenon normally associated to shear flows. Chapter 2 extends analytical tools available only for elementary polymer models or for steady flows to general bead-rod-spring models in random flows. By building on the results from the previous chapters, Chap. 3 culminates with the study of an unexplored Lagrangian degree of freedom in a turbulent flow: bending. A semiflexible particle is shown to display different bending behaviours in two- and three-dimensional random flows. This prediction is confirmed via direct numerical simulations of the particle in a turbulent flow. Part II concerns “elastic turbulence", a chaotic regime created in a flow with low inertial forces by the addition of elastic polymers. Chapter 4 provides an estimate for the number of degrees of freedom of a solution of this chaotic system via the Lyapunov dimension of the attractor of the two-dimensional Oldroyd-B model, a model known to reproduce elastic turbulence in numerical simulations. Chapter 5 questions the necessity of elasticity in producing a chaotic regime and concludes that a rodlike polymer solution can create a regime similar to elastic turbulence.Les particules soumises à un écoulement peuvent manifester des orientations préférées et une variété de déformations en fonction de leur géométrie et élasticité et du champ de vitesse de l'écoulement. A l’inverse, les flux peuvent être modifiés lorsque les contraintes des particules sont non négligeables. Cette thèse présente des résultats théoriques et numériques sur cette relation bilatérale en deux parties. La Ière partie commence par une analyse de stabilité et des simulations numériques qui montrent une particule brownienne semi-flexible dans un écoulement élongationnel effectuant un retournement, un phénomène associé aux flux de cisaillement. Le Chap. 2 étend les outils analytiques dédiés aux modèles simples ou aux flux indépendante du temps pour les modèles perle-barre-bond généraux dans les flux aléatoires. En partant des résultats des chapitres précédents, Le Chap. 3 aboutit à l'étude d'un degré de liberté lagrangien inexploré dans un écoulement turbulent : la flexion. Une particule semi-flexible courbe différemment dans les flux aléatoires bidimensionnels et tridimensionnels. La IIème partie concerne la turbulence élastique, un régime chaotique créé dans un écoulement de faibles forces inertielles par l'ajout de polymères élastiques. Le Chap. 4 estime le nombre de degrés de liberté d'une solution de ce régime via la dimension Lyapunov de l'attracteur du modèle Oldroyd-B bidimensionnel, un modèle connu de reproduire la turbulence élastique dans les simulations numériques. Le Chap. 5 pose des questions sur la nécessité d'élasticité pour produire un régime chaotique et conclut qu'une solution de polymère de barres peut créer un régime comparable à la turbulence élastique
LDScript: a Linked Data Script Language
No full textInternational audienceIn addition to the existing standards dedicated to representation or querying, Semantic Web programmers could really benefit from a dedicated programming language enabling them to directly define functions on RDF terms, RDF graphs or SPARQL results. This is especially the case, for instance, when defining SPARQL extension functions. The ability to capitalize complex SPARQL filter expressions into extension functions or to define and reuse dedicated aggregates are real cases where a dedicated language can support modularity and maintenance of the code. Other families of use cases include the definition of functional properties associated to RDF resources or the definition of procedural attachments as functions assigned to RDFS or OWL classes with the selection of the function to be applied to a resource depending on the type of the resource. To address these needs we define LDScript, a Linked Data script language on top of the SPARQL filter expression language. We provide the formal grammar of the syntax and the Natural Semantics inference rules of the semantics of the language. We also provide a benchmark and perform an evaluation using real test bases from W3C with different implementations and approaches comparing, in particular, script interpretation and Java compilation
Stereodynamic control of star-epoxy/anhydride crosslinking actuated by liquid-crystalline phase transitions.
No full textInternational audienceThe epoxy/anhydride copolymerization kinetics of an original star-epoxy monomer (TriaEP) was explored in dynamic heating mode using a series of isoconversional methods. Negative values of the apparent activation energy (Eα) related to an anti-Arrhenius behavior were observed. The transition from Arrhenius to anti-Arrhenius behavior and vice versa depending on the Eα of polymerization was correlated with the dynamics of mesophasic fall-in/fall-out events, physically induced transition (PIT) and chemically induced transition (CIT). This self-assembly phenomenon induces the generation of an anisotropic crosslinked architecture exhibiting both nematic discotic (ND) and nematic columnar (NC) organization. Particular emphasis was placed on evaluating the juxtaposition/contribution of the liquid-crystalline transitions to crosslinking, considering both the reaction dynamics and the macromolecular vision
PAH features within few hundred parsecs of active galactic nuclei
No full textInternational audienceSpectral features from polycyclic aromatic hydrocarbon (PAH) molecules observed in the mid-infrared (mid-IR) range are typically used to infer the amount of recent and ongoing star formation on kiloparsec scales around active galactic nuclei (AGN) where more traditional methods fail. This method assumes that the observed PAH features are excited predominantly by star formation. With current ground-based telescopes and the upcoming James Webb Space Telescope, much smaller spatial scales can be probed and we aim at testing if this assumption still holds in the range of few tens to few hundreds of parsecs. For that, we spatially map the emitted 11.3 μm PAH surface flux as a function of distance from 0.4–4 arcsec from the centre in 28 nearby AGN using ground-based high-angular-resolution mid-IR spectroscopy. We detect and extract the 11.3 μm PAH feature in 13 AGN. The fluxes within each aperture are scaled to a luminosity-normalized distance from the nucleus to be able to compare intrinsic spatial scales of AGN radiation spanning about two orders of magnitude in luminosity. For this, we establish an empirical relation between the absorption-corrected X-ray luminosity and the sublimation radius in these sources. Once normalized, the radial profiles of the emitted PAH surface flux show similar radial slopes, with a power-law index of approximately −1.1, and similar absolute values, consistent within a factor of a few of each other as expected from the uncertainty in the intrinsic scale estimate. We interpret this as evidence that the profiles are caused by a common compact central physical process, either the AGN itself or circumnuclear star formation linked in strength to the AGN power. A photoionization-based model of an AGN exciting dense clouds in its environment can reproduce the observed radial slope and confirms that the AGN radiation field is strong enough to explain the observed PAH surface fluxes within ∼10–500 pc of the nucleus. Our results advice caution in the use of PAH emission as a star formation tracer within a kpc around AGN