PECTOLYTIC ENZYMES FROM INTERACTIONS BETWEEN PSEUDOMONAS-SYRINGAE PV PHASEOLICOLA AND FRENCH BEAN (PHASEOLUS-VULGARIS)

Pectolytic enzymes were extracted from both compatible and incompatible interactions between Pseudomonas syringae pv. phaseolicola and French bean. Much lower levels of activity were obtained from control, buffer-inoculated leaves. Temperature and pH optima were similar for enzyme extracted from both inoculated and control leaves. Temperature and pH profiles were similar for enzymes from compatible and incompatible interactions, but different from those of the controls. Enzyme activity in inoculated leaves did not increase until 20 h after inoculation, but then increased rapidly over the succeeding 2-3 days. Activity from control leaves had increased marginally by 48 h after inoculation, but then decreased to about 50 % of the original level. Enzymes from incompatible and compatible interactions both had pI values of 7.7. Substrate degradation studies and analysis of reaction products indicated that the enzymes were endopolygalacturonases. HPLC indicated that the enzyme from the compatible interaction had a relative molecular mass of approximately 44,000. When injected into leaves the partially purified enzyme was a potent elicitor of phytoalexin accumulation.