Isoperoxidase Involvement in the Resistance of Capsicum annuum to Infection by Cucumber Mosaic Virus

Cucumber mosaic virus (CMV) infection of Capsicum annuum leaves provokes a strong increase in soluble peroxidase activity. Isoelectrofocusing of the peroxidase activity in polyacrylamide gel patterns, after staining the soluble protein fractions from both healthy and infected leaves with benzidine/H 2O 2, revealed the presence of two acidic and one basic isoperoxidases, the increase in peroxidase activity being mainly due to the former. Staining of peroxidase activity in the gels with coniferyl alcohol/H 2O 2 showed that acidic isoenzymes were more capable of catalyzing coniferyl alcohol oxidation than basic isoenzymes. Native polyacrylamide gel electrophoresis of the soluble fraction showed that the increase in peroxidase isoenzymes. CMV elicitation of the acidic isoperoxidase through its involvement in the lignification process might be considered as a part of the defense mechanism of Capsicum annuum against viral infection, lignin deposition on plasmodesmata could act as a physical barrier against the cell-to-cell advance of viral particles.