Activation of cell wall-associated peroxidase isoenzymes in pea epicotyls by a xyloglucan-derived nonasaccharide

Abstract

The cell wall-derived xyloglucan nonasaccharide XXFG was found to increase the extractable activity of distinct cationic cell wall-associated peroxidase isozyme groups isolated from etiolated pea epicotyls. Peroxidase activation occurred in the first 10 h of incubation with the nonasaccharide in the pea epicotyl bioassay. At the same time varying concentrations of XXFG caused growth inhibition up to 35%. Neither the increase of peroxidase activity nor the growth inhibition was restricted to a certain XXFG concentration. The increase in peroxidase activity was not just an oligosaccharide effect in general. The corresponding heptasaccharide XXXG neither inhibited growth nor increased peroxidase activity. The isozymes extracted from pea epicotyls were additionally separated by cation-exchange chromatography and submitted to isoelectric focusing. With one exception, all of the ionically-bound, cell wall-associated peroxidases present in pea epicotyls were cationic or slightly anionic. It is proposed that the growth inhibition caused by XXFG is at least in part the result of peroxidase- catalysed cell wall tightening induced by the nonasaccharide.