An Endogenous Suppressor of the Defense Response in <italic>Pisum sativum</italic>

Abstract

Healthy pea plants contain a substance, tentatively called “endogenous suppressor”, which specifically suppresses the accumulation of pisatin in pea plants that is induced by treatment with CuCl2 or an elicitor from Mycosphaerella pinodes. This suppressor elicits the accumulation of phytoalexins in other legumes, such as kidney bean, soybean and cowpea. The endogenous suppressor functions to delay the accumulation of pisatin, the activation of phenylalanine ammonialyase (PAL) and the accumulation of mRNAs for PAL and chalcone synthase induced by the elicitor from M. pinodes. The substance specifically induces susceptibility to nonpathogens, such as Mycosphaerella ligulicola and M. melonis, in pea out of four species of legume tested, but the effect is not cultivar-specific. Thus, the endogenous suppressor in healthy pea plants suppresses a series of self-defense reactions and induces susceptibility in pea plants in a species-specific manner, being similar to the exogenous fungal suppressor from the pea pathogen, M.pinodes.