Antonio Valera Espín

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

Summary 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 2 O 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 2 O 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.

Soluble pathogenesis-related proteins ofCapsicum annuum leaves induced by cucumber mosaic virus infection

Eight major pathogenesis related (PR) proteins were found in a soluble extract of cucumber mosaic virus (CMV) infectedCapsicum annuum leaves. None of them was present in the soluble extract of sham-inoculated controls. The proteins were detected by two-dimensional polyacrylamide gel electrophoresis using (2D-PAGE)PhastSystem, native-PAGE in the first dimension and SDS-PAGE in the second. Two major acidic PR-proteins were identified on the basis of their relative molecular mass (Mr), PR1 of 15.3 kD and PR2 of 29 kD. Six proteins were basic and were identified as PRla of 15.9 kD, PRlb of 15.0 kD, PRlc of 15.9 kD, PR2 of 27.0 kD, PR3 of 36.3 kD and PR4 of 48.8 kD.