INVOLVEMENT OF FREE CALCIUM IN ACTION OF CRYPTOGEIN, A PROTEINACEOUS ELICITOR OF HYPERSENSITIVE REACTION IN TOBACCO CELLS

Treatment of suspension-cultured tobacco (Nicotiana tabacum var, Xanth i) cells with cryptogein, a proteinaceous elicitor from Phytophthora c ryptogea, induced a great stimulation of Ca2+ influx within the first minutes. Ca2+ influx is essential for the initiation of cryptogein-ind uced responses, since ethyleneglycol-bis(beta-amino-ethyl ether)-N,N'- tetraacetic acid or La3+, which block Ca2+ entrance, suppress cryptoge in-induced responses such as extracellular alkalinization, active oxyg en species, and phytoalexin production. Moreover, once initiated, thes e responses require sustained Ca2+ influx within the Ist h. A Ca2+ ion ophore (A23187) was able to trigger an extracellular alkalinization bu t not the formation of active oxygen species and phytoalexins, even in the presence of cryptogein. Staurosporine, a protein kinase inhibitor that was recently reported to suppress cryptogein-induced responses ( M.-P. Viard, F. Martin, A. Pugin, P. Ricci, J.-P. Blein [1994] Plant P hysiol 104: 1245-1249), inhibited Ca2+ influx induced by cryptogein in a dose-dependent manner. These results suggest that protein phosphory lation followed by Ca2+ influx might be involved in the initial steps of cryptogein signal transduction.