Altered matrix polysaccharides in cell walls of pocket galls formed by an aphid on Distylium racemosum leaves

Abstract

The present work reports the results of a study on the isolation and characterization of matrix polysaccharides in the cell walls of galls formed by an aphid (Neothoracaphis yanonis) on Distylium racemosum leaves. Cell walls were isolated from both healthy Distylium leaf and gall tissues and then extracted sequentially with cyclohexane-frans-1,2-diaminetetra-acetate (CDTA), Na2CO3, 1 M KOH, and 4 M KOH. The amount of pectin solubilized from gall cell walls was approximately 2.6-fold higher than the pectin solubilized from leaf cell walls, whereas the amount of hemicellulose solubilized from gall cell walls was 1.4-fold higher than that from normal leaf cell walls. When the polysaccharides were fractionated by anion-exchange chromatography, considerable increases in arabinose and galactose were observed in CDTA-soluble pectic polymer (fraction PI-1) from gall cell walls, whereas the gall cell walls had less xylose in 1 M KOH-soluble hemicellulosic polymers (fractions HI-2, HI-3, and HI-4) than did the cell walls from the healthy leaf. The hemicellulosic polymers of the gall cell walls exhibited distinctly different patterns of molecular mass, compared with the healthy leaf cell walls. These results suggest that an extensive change occurs in the matrix polysaccharide structure of the cell walls of Distylium galls formed by an aphid. In addition, many glycosylhydrolase activities were detected in the protein fraction solubilized with strong saline solution from the gall cell walls, and the activities of β-galactosidase, β-xylosidasc and α-L-arabinofuranosidase were considerably increased under gall formation.