Xyloglucan for Generating Tensile Stress to Bend Tree Stem

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G （gelatinous）-Iayer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase （XET） activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide （XXXG） for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer micro fibrils.     

Wnt9b plays a central role in the regulation of mesenchymal to epithelial transitions underlying organogenesis of the mammalian urogenital system

The vertebrate urogenital system forms due to inductive interactions between the Wolffian duct, its derivative the ureteric bud, and their adjacent mesenchymes. These establish epithelial primordia within the mesonephric (embryonic) and metanephric (adult) kidneys and the Müllerian duct, the anlage of much of the female reproductive tract. We show that Wnt9b is expressed in the inductive epithelia and is essential for the development of mesonephric and metanephric tubules and caudal extension of the Müllerian duct. Wnt9b is required for the earliest inductive response in metanephric mesenchyme. Further, Wnt9b-expressing cells can functionally substitute for the ureteric bud in these interactions. Wnt9b acts upstream of another Wnt, Wnt4, in this process, and our data implicate canonical Wnt signaling as one of the major pathways in the organization of the mammalian urogenital system. Together these findings suggest that Wnt9b is a common organizing signal regulating diverse components of the mammalian urogenital system.     

Efficient gene modulation in mouse epiblast using a Sox2Cre transgenic mouse strain

We have generated a transgenic line that expresses the Cre gene product under the regulation of a 12.5 kb upstream regulatory sequence from the Sox2 gene. Using a R26R reporter line, we show that this transgenic line induces recombination in all epiblast cells by embryonic day (E) 6.5 but little or no activity in other extraembryonic cell types at this time. When crossed to a conditional allele of the Sonic hedgehog gene (Shhc), all Sox2Cre;Shhn/Shhc embryos displayed a phenotype indistinguishable from that of the Shh null mutant. Sox2Cre functioned more efficiently in epiblast-mediated recombination than the Mox2Cre (MORE) transgenic line, which has also been shown to drive Cre-mediated recombination exclusively in the embryonic component of the early mouse embryo. Although most MORE; shhh/shhc embryos have a shh hull phenotype, 33% displayed a milder skeletal phenotype, most likely result of incomplete recombination at egg cylinder stages. In agreement with these findings, Sox2Cre was active earlier and Sox2Cre-mediated recombination was more advanced than MORE-mediated recombination at early gastrulation stages. The Sox2Cre line is likely to be more effective in generating complete, epiblast-specific removal of gene activity, and the mosaic activity of the MORE line will be helpful in generating partial loss-of-function phenotypes in the embryo-proper.     

Glycoprotein mannosylation in rat liver nuclei

Nuclei and non-nuclear membranes were tested for their ability to transfer in vitro (14C)mannose from GDP-(14C)mannose to endogenous glycoprotein acceptors in the presence and in the absence of exogenous retinyl-phosphate. Electrophoretic analysis shows that retinylphosphate is responsible for the labeling of a few endogenous acceptors only in the non-nuclear membranes; in the nuclei the mannosylation reaction is not retinylphosphate dependent and the electrophoretic profile of the labeled protein acceptors is different from that of the non-nuclear membranes.     

Influence of acclimation temperature on GDP-mannose: Dolicholphosphate mannosyltransferase of trout liver (Salmo Gairdneri)

Mannosyltransferase activity has been studied in trout liver microsomes prepared from fish adapted during 1 month at three different temperatures: 7, 15 and 21°C; the purpose of the study was to try and answer this question: is the enzyme sensitive to temperature variations and if so, do optimum pH variations reflect an adaptation to temperature changes? The following effects were observed: 1. Optimum pH values do not vary significantly with incubation temperature; only a discrete shift towards more acidic pH has been observed for trouts raised at 21°C. 2. For trouts raised at 7 and 15°C, the enzymic activity increases slightly with incubation temperature while it remains constant for the trouts acclimated at 21°C. This observation could be explained by a lower level of endogenous dolicholphosphate. 3. At any incubation temperature, the higher the acclimation temperature, the lower the enzymic activity.     

Pyrolysis of Cellulose

The volatile compounds such as acetaldehyde, propionaldehyde, acrolein, acetone, diacetyl, furan, furfural and 5-methyl furfural from cellulose, cellobiose, glucose and levoglucosan pyrolysates at 250°C, 350°C and 500°G were studied by gas chromatography with a pyrolyzer without intermediate trapping. The composition of the volatiles was changed with the temperatures and the degradation stages of cellulose pyrolysis.

Analytical data of the relative amounts of the volatiles show that pyrolysis of cellulose proceeds through two primary simultaneous reactions: a) the initial scission of glucosidic linkages, and b) chemical changes in anhydroglucose units of cellulose.     

Effet de proteines basiques de faible poids moleculaire sur le transfert de mannose dans les microsomes d'Aspergillus niger

Basic proteins of low molecular weight activate the transfer of mannose to endogenous glycoprotein acceptors in microsomal membranes of Aspergillus niger. The enhancement of mannosyltransferase activity is linked to the activation of the transport of mannose across the membrane. The role of these polycationic proteins on the membrane permeability is discussed.