Phytophthora parasitica elicitor-induced reactions in cells of Petroselinum crispum

Cultured parsley (Petroselinum crispum) cells respond to treatment with eli citors derived from different species of the genus Phytophthora with transc ript accumulation of defense-associated genes and the production of furanoc oumarin phytoalexins, Pep-25, an oligopeptide fragment of a Phytophthora so jae 42-kDa cell wall protein, and a cell wall elicitor preparation derived from Phytophthora parasitica (Pp-elicitor) stimulate accumulation of the sa me gene transcripts and formation of the same pattern of furanocoumarins, T reatment of cultured cells and protoplasts with proteinase-digested Pp-elic itor identified proteinaceous constituents as active eliciting compounds in parsley, Similar to Pep- 25, Pp-elicitor induced effluxes of K+ and Cl- an d influxes of protons and Ca2+. Concomitantly, as monitored in aequorin-tra nsgenic parsley cell lines both elicitors induced an immediate increase in the cytoplasmic Ca2+ concentration up to sustained levels of 175 nM (Pp-eli citor) or 300 nM (Pep-25), respectively. The signature of the Ca2+ response differed greatly between the two elicitors tested. Extracellular Ca2+ prov ed essential for activation of an oxidative burst, MAP kinase activity and phytoalexin production by either elicitor. While Ppelicitor induced a quali tatively similar spectrum of defense responses as did Pep-25, elicitor-spec ific quantitative differences in response intensity and kinetics suggest ac tivation of a conserved signaling cascade through separate ligand binding s ites.