Abstract
Healthy pea plants contain a factor, as called an endogenous suppressor, which suppresses the accumulation of pisatin induced by the elicitor from a pea pathogen, Mycosphaerella pinodes. The effects of the endogenous suppressor on the activation of pathogenesis-related proteins (PR-proteins) such as chitinase and β-1, 3-glucanase were examined. The fungal elicitor induced the activations of these enzymes in pea, kidney bean and soybean, however, the concomitant presence of the endogenous suppressor with the fungal elicitor resulted in suppression of activations of these enzymes in only pea but not in kidney bean or soybean. In contrast, the endogenous suppressor alone rather activated these enzymes in kidney bean and soybean to which M. pinodes is nonpathogenic. Thus, the action of endogenous suppressor on the activation of PR-proteins is species-specific as well as that on the production of phytoalexins. Together with our previous report, these findings show that the pea endogenous suppressor may have a potential to block the general resistance of its producer and that it is quite similar to the exogenous suppressor from M. pinodes with respect to the biological activities.
