2 CHAINS OF RHAMNOGALACTURONAN-II ARE CROSS-LINKED BY BORATE-DIOL ESTER BONDS IN HIGHER-PLANT CELL-WALLS

Polysaccharide moiety of the boron-polysaccharide complex (T. Matoh, K . Ishigaki, K. Ohno, J. Azuma [1993] Plant Cell Physiol 34: 639-642) i solated from radish (Raphanos sativus) roots has been shown to be rham nogalacturonan II by glycosyl-linkage analysis and the presence of dia gnostic monosaccharides, including apiose, aceric acid, 2-O-methylfuco se, and 3-deoxy-D-manno-2-octulosonic acid. Removal of boron from the complex reduced the molecular weight by one-half without causing a sig nificant increase in the number of reducing end groups, indicating tha t boron, as boric acid, links two rhamnogalacturonan II chains togethe r to form the boron-polysaccharide complex.