Structure of the Primary Cell Walls of Suspension-Cultured Rosa glauca Cells

摘要

Xyloglucans, characteristic hemicellulosic polysaccharides of plant primary walls, have been isolated from Rosa glauca suspension-cultured cells. The cell wall material was fractionated by two sequences of extraction based on solubilization of the hemicelluloses in alkaline and organic solvent systems, respectively. In both cases, only a part (about 50%) of the total xyloglucan could be extracted, the rest remaining tightly associated with cellulose and necessitating the use of acid to be solubilized. Purification of xyloglucans was effected by formation of a gel in appropriate mixtures of dimethyl sulfoxide and water. Further fractionation could be achieved on a cellulose column eluted with chaotropic solvents. This demonstrated the heterogeneity of xyloglucans in the primary cell walls. Analytical data show that all fractions are constituted with the same sugars: l-arabinose, l-fucose, d-galactose, d-xylose, and d-glucose, but their relative proportions differ, particularly the ratio of glucose to xylose which varies from 1.2 to 2 within the different xyloglucans. The structure of these hemicelluloses was established by methylation analysis and shown to consist of a (1 → 4)-linked glucan backbone which carries substituents on the O-6 of glucose. Here again, the multiple forms of xyloglucans was suggested by the various patterns of substitutions found on the different fractions. The configuration of the linkages were established by ¹³C nuclear magnetic resonance spectroscopy and shown to be β for the glucan backbone, α for the xylosyl and fucosyl substituents, and β for the galactosyl substituents. These configurations agree with the specific rotation of the xyloglucan.