Hydrogen peroxide is required for poly(phenolic) domain formation during wound-induced suberization

The requirement for hydrogen peroxide (H(2)O(2)) during suberization was demonstrated in wound-induced potato tubers by monitoring the extent of phenolic polymerization after the inhibition of H(2)O(2) production using diphenyleneiodonium (DPI). In DPI-treated tissues the extent of phenolic polymerization in suberized tissues, measured using DFRC (Derivatization Followed by Reductive Cleavage) and thioglycolic acid analyses, was greatly reduced relative to untreated controls. Concomitantly, a large quantity of new soluble phenolics accumulated in the DPI-treated tissue some of which were not present in the controls. We suggest that the inhibition of H(2)O(2) production prevented these phenolics from being oxidized by cell wall peroxidases. As a result, these phenolics were left unpolymerized and accumulated in the tissue. Several of the soluble phenolics were identified as hydroxycinnamic acid derivatives. From the data presented, it was concluded that H(2)O(2) is required for the polymerization step in the formation of the poly(phenolic) domain of suberized potato tubers.