Academic literature on the topic 'Xyloglucanes fucosylés'

Rate-zonal centrifugation of pea (Pisum sativum var. Alaska) stem microsomal membranes on a linear Renografln gradient separated Golgi secretory vesicles from dictyosomes. Secretory vesicles possessed high levels of xyloglucan fucosyl transferase activity, which effects the final decoration of stem xyloglucan side-chains, but lacked substantial xyloglucan xylosyl transferase activity, which is required for the synthesis of the xyloglucan backbone. In contrast, total dictyosomal membranes possessed both fucosyl and xylosyl transferase activities. Isopycnic centrifugation of a homogenized dictyosome-enriched membrane preparation on a shallower Renografln gradient indicated that lighter dictyosomal membranes possessed xylosyl transferase but relatively little fucosyl transferase activity. The bulk of the dictyosomal membranes formed a denser peak in which xylosyl and fucosyl transferase activities codistributed. Thus a differential localization of function in the Golgi apparatus during biosynthesis of xyloglucan is indicated. A tentative mechanism is suggested in which the elaboration of the glucose-xylose backbone is initiated in lighter dictyosomal membranes, backbone synthesis is concluded and fucosylation begun in denser dictyosomal membranes, and fucosylation completed in Golgi secretory vesicles during transport of xyloglucan to the cell wall.

Immunolabeling and transmission electron microscopic techniques were used to investigate the chemical nature of wall appositions in roots of susceptible and resistant soybean plants inoculated with Phytophthora sojae race 2. The extrahaustorial matrix associated with the haustorium of Phytophthora sojae also was examined. Antibodies against (1 → 3)-β-glucan, a terminal α-fucosyl-containing epitope present in xyloglucan and rhamnogalacturonan I, and an arabinosylated (1 → 6)-β-galactan epitope present in arabinogalactan proteins were used. (1 → 3)-β-Glucan (callose), xyloglucan, and arabinogalactan proteins were found to be localized in all wall appositions regardless of how long after inoculation the appositions developed or whether plants were susceptible or resistant to Phytophthora sojae. (1 → 3)-β-Glucan also was found in fungal walls and at host cell plasmodesmata. None of the four antibodies labeled the extrahaustorial matrix. The antibody against arabinogalactan protein recognized the host plasma membrane, but not the invaginated host plasma membrane associated with the extrahaustorial matrix. This result indicates that the properties or the composition of the host plasma membrane may change locally once it becomes an extrahaustorial membrane. Key words: Phytophthora sojae, Glycine max, callose, immunolabeling, wall appositions, papillae.

The natural trait variation in Arabidopsis thaliana (L.) Heynh. accessions is an important resource for understanding many biological processes but it is underexploited for wood-related properties. Twelve A. thaliana accessions from diverse geographical locations were examined for variation in secondary growth, biomechanical properties, cell wall glycan content, cellulose microfibril angle (MFA) and flowering time. The effect of daylength was also examined. Secondary growth in rosette and inflorescence stems was observed in all accessions. Organised cellulose microfibrils in inflorescence stems were found in plants grown under long and short days. A substantial range of phenotypic variation was found in biochemical and wood-related biophysical characteristics, particularly for tensile strength, tensile stiffness, MFA and some cell wall components. The four monosaccharides galactose, arabinose, rhamnose and fucose strongly correlated with each other as well as with tensile strength and MFA, consistent with mutations in arabinogalactan protein and fucosyl- and xyloglucan galactosyl-transferase genes that result in decreases in strength. Conversely, these variables showed negative correlations with lignin content. Our data support the notion that large-scale natural variation studies of wood-related biomechanical and biochemical properties of inflorescence stems will be useful for the identification of novel genes important for wood formation and quality, and therefore biomaterial and renewable biofuel production.

La xylogenèse conduit entre autres à la formation de fibres et de vaisseaux impliquant une cascade d'évènements dont notamment la mise en place d'une paroi secondaire. Cependant, sous les effets de contraintes environnementales (vent, pente), une nouvelle architecture de cette paroi est observée. Celle-ci va influer directement sur les propriétés mécaniques et la qualité du bois. Afin de restaurer la verticalité de leur tige, les angiospermes ligneuses développent en effet un bois particulier appelé le « bois de tension » qui se caractérise par la formation d'une strate atypique : la « couche gélatineuse ». Par des techniques de biochimie et de biologie moléculaire chez le peuplier hybride (Populus tremula x Populus alba, clone INRA 717-1-B4), et afin de mettre en évidence certains mécanismes moléculaires impliqués dans la formation de ce bois, nous avons cherché à isoler et caractériser deux groupes d'enzymes –des β(1,4)-xylosidases et des α(1,2)-fucosyltransférases- impliqués dans le réarrangement et la biosynthèse des xylanes et xyloglucanes respectivement. Deux de ces enzymes, PtaBXL1 et PtaFUT1, apparaissent ainsi sous-exprimées spécifiquement dans la zone de bois de tension. En parallèle, nous avons développé un modèle d'étude in vitro de formation du bois de tension dans le but de réaliser un état des lieux par immunohistochimie et diverses colorations des différents polymères pouvant être impliqués dans la formation et les propriétés mécaniques de ce bois particulier. Des AGPs et des RG-I ont ainsi été trouvés au sein de la couche G, ce qui suggère leur participation au développement des forces de tension dans le redressement des tiges
Xylogenesis leads among others to the formation of fibers and vessels which involves a cascade of events including the establishment of a secondary wall. However, under the effects of environmental constraints (wind, slope), a new architecture of this wall is observed. This last one will directly affect the mechanical properties and wood quality. In order to reinstate verticality of their stems, the woody angiosperms develop a particular wood called “tension wood” which is characterized by the formation of an atypical layer : the “gelatinous layer”. By techniques of biochemistry and molecular biology on the hybrid poplar (Populus tremula x Populus alba, clone INRA 717-1-B4), and in order to highlight some molecular mechanisms involved in the formation of this wood, we have sought to isolate and characterize two groups of enzymes -β(1,4)-xylosidases and α(1,2)-fucosyltransferases- involved in the rearrangement and the biosynthesis of xylans and xyloglucans respectively. Two of these enzymes, PtaBXL1 and PtaFUT1, appear down-regulated specifically in tension wood. In parallel, we developed a study model in vitro of formation of tension wood in order to carry out an inventory by immunohistochemistry and various staining of the different polymers that may be involved in the formation and mechanical properties of this particular wood. Also, AGPs and RG-I has been found in G layer, which suggests their participation in the development of tension forces in straightening of stems