Characterization of the cell wall matrix polysaccharides and glycoside-hydrolyzing enzymes of Distylium racemosum callus

Abstract

The non-cellulosic (matrix) polysaccharides found in the cell walls of callus tissues derived from healthy Distylium racemosum leaves have been analyzed in this study. The amounts of rhamnose, arabinose, and glucose in the cell walls increased 2-fold over the culture period of 70 d, but galactose content remained more or less constant. Comparisons were also made among the polysaccharides found in callus tissues, those from healthy leaves, and those from aphid-induced galls in D. racemosum leaves. After successive extraction with 50 mM CDTA, 50 mM Na 2CO 3, 1 M KOH, and 4 M KOH, the amounts of pectic fractions (CDTA- and Na 2CO 3-soluble) from the cell walls of callus, gall, and leaf tissues accounted for 17%, 11%, and 4%, respectively, of cell wall dry weight. The callus cell walls had less xylose in 4 M KOH-soluble polymers (HII-2 and HII-3) fractionated by anion-exchange chromatography than did the cell walls from healthy leaves. Polysaccharides in fractions HII-2 and HII-3 from callus cell walls were subfractionated into the void fraction, a 250 kDa fraction, and a 40 kDa fraction by size-exclusion chromatography. These results appear to more closely resemble the situation in the aphid-induced gall tissues than that in the leaf tissues. In addition, the activities of β-xylosidase and α- l-arabinofuranosidase in the LiCl-soluble protein fraction increased notably during callus development.