CHARACTERIZATION OF EXTRACELLULAR BETA(1,4)-XYLAN BACKBONE O-SUBSTITUTED BY ARABINOGALACTANS TYPE-II IN A PLANT-CELL SUSPENSION

In this paper we demonstrate for the first time the existence of an et her linkage between arabinogalactans type II (AGII) and a beta(1,4)-xy lan backbone. This polysaccharide fraction was isolated by ethanolic p recipitation from a culture medium of Silene alba cells suspension. A combination of chromatographic methods, the use of a pure specific xyl anase and the determination of the reducing end, has enabled us to est ablish the orientation of the linkage. The results were confirmed by m ethylation analysis assisted by mass spectrometry and by C-13-NMR spec troscopy. The proposed xylan structure is a beta(1,4)-xylan backbone c arrying AGII side chains of different sizes which are interspersed alo ng the xylan chain. Such a result may be considered as an additional a rgument for supporting the importance of AGII in plant cell biology.