A boron-rhamnogalacturonan-II complex from bamboo shoot cell walls

A boron-polysaccharide complex was isolated from a Driselase digest of bamboo (Phyllostachys edulis) shoot cell walls by successive DEAE Sepharose FF, Bio-Gel P-10 and Mono Q HR 5/5 chromatography. The complex contained 0.15% boron (w/w). The glycosyl residue and linkage composition analyses of the polysaccharide moiety of the complex identified the polysaccharide as a rhamnogalacturonan-II (RG-II), a structurally complex pectic polysaccharide present in the primary cell walls of all higher plants. B-11 NMR spectroscopy showed that boron was present as a tetrahedral borate-diol diester. Removal of boron from the complex decreased the M(r) by half without any loss of glycosyl residues, suggesting that boron cross-links two RG-II molecules. The boron-RG-II complex from bamboo (a monocot) shoot cell walls has almost the same structure as that of sugar beet (a dicot) cell walls. The results demonstrate that the structure of boron-RG-II complex is very similar in dicots and monocots. Copyright (C) 1996 Elsevier Science Ltd