Étude des paramètres ayant une influence sur le comportement au fluage d’un sable injecté

Le comportement au fluage du sable de Fontainebleau injecté par un gel de silice, chimiquement instable est comparé au comportement au fluage du même sable injecté par deux coulis de nouvelle génération chimiquement stables, un coulis de ciment micro-fin et un coulis minéral. Le comportement au fluage est caractérisé par des essais en compression simple et des essais avec confinement réalisés sur des périodes allant de 100 à 200 jours. Les résultats sont analysés en termes de pente de fluage et de charge limite de fluage. L’analyse des essais a mis en évidence que le mode de mise en place du sable joue un rôle important sur les déformations de fluage du sable injecté. Les déformations de fluage sont considérablement réduites par l’application d’une contrainte de confinement. Le traitement d’injection modifie le comportement au fluage du sable : selon la nature du coulis injecté, le sable injecté présente des déformations de fluage plus ou moins importantes. Les pentes de fluage du sable injecté sont proportionnelles aux pentes de fluage du coulis pur. Les caractéristiques au fluage du sable injecté semblent ainsi pouvoir être déduites du comportement au fluage du sable non traité et du comportement au fluage du coulis pur

Investigating the molecular mechanism of the self-incompatility response in Brassica

International audienc

The S15 self-incompatibility haplotype in Brassica oleracea includes three S gene family members expressed in stigmas.

Self-incompatibility in Brassica is controlled by a single, highly polymorphic locus that extends over several hundred kilobases and includes several expressed genes. Two stigma proteins, the S locus receptor kinase (SRK) and the S locus glycoprotein (SLG), are encoded by genes located at the S locus and are thought to be involved in the recognition of self-pollen by the stigma. We report here that two different SLG genes, SLGA and SLGB, are located at the S locus in the class II, pollen-recessive S15 haplotype. Both genes are interrupted by a single intron; however, SLGA encodes both soluble and membrane-anchored forms of SLG, whereas SLGB encodes only soluble SLG proteins. Thus, including SRK, the S locus in the S15 haplotype contains at least three members of the S gene family. The protein products of these three genes have been characterized, and each SLG glycoform was assigned to an SLG gene. Evidence is presented that the S2 and S5 haplotypes carry only one or the other of the SLG genes, indicating either that they are redundant or that they are not required for the self-incompatibility response

The receptor kinases LePRK1 and LePRK2 associate in pollen and when expressed in yeast, but dissociate in the presence of style extract

After pollen grains germinate on the stigma, pollen tubes traverse the extracellular matrix of the style on their way to the ovules. We previously characterized two pollen-specific, receptor-like kinases, LePRK1 and LePRK2, from tomato (Lycopersicon esculentum). Their structure and immunolocalization pattern and the specific dephosphorylation of LePRK2 suggested that these kinases might interact with signaling molecules in the style extracellular matrix. Here, we show that LePRK1 and LePRK2 can be coimmunoprecipitated from pollen or when expressed together in yeast. In yeast, their association requires LePRK2 kinase activity. In pollen, LePRK1 and LePRK2 are found in an ≈400-kDa protein complex that persists on pollen germination, but this complex is disrupted when pollen is germinated in vitro in the presence of style extract. In yeast, the addition of style extract also disrupts the interaction between LePRK1 and LePRK2. Fractionation of the style extract reveals that the disruption activity is enriched in the 3- to 10-kDa fraction. A component(s) in this fraction also is responsible for the specific dephosphorylation of LePRK2. The style component(s) that dephosphorylates LePRK2 is likely to be a heat-stable peptide that is present in exudate from the style. The generally accepted model of receptor kinase signaling involves binding of a ligand to extracellular domains of receptor kinases and subsequent activation of the signaling pathway by receptor autophosphorylation. In contrast to this typical scenario, we propose that a putative style ligand transduces the signal in pollen tubes by triggering the specific dephosphorylation of LePRK2, followed by dissociation of the LePRK complex