Induction of H2O2 synthesis by beta-glucan elicitors in soybean is independent of cytosolic calcium transients

Soybean cell suspension cultures have been used to investigate the role of the elevation of the cytosolic Ca2+ concentration in beta -glucan elicitors -induced defence responses, such as H2O2 and phytoalexin production. The in tracellular Ca2+ concentration was monitored in transgenic cells expressing the Ca2+-sensing aequorin. Two lines of evidence showed that a transient i ncrease of the cytosolic Ca2+ concentration is not necessarily involved in the induction of H2O2 generation: (i) a Bradyrhizobium japonicum cyclic bet a -glucan induced the H2O2 burst without increasing the cytosolic Ca2+ conc entration; (ii) two ion channel blockers (anthracene-9-carboxylate, A9C, 5- nitro-2-(3-phenylpropylamino)-benzoate, NPPB) could not prevent a Phytophth ora soja beta -glucan elicitor-induced H2O2 synthesis but did prevent a cyt osolic Ca2+ concentration increase. Moreover, A9C and NPPB inhibited A soja e beta -glucan-elicited defence-related gene inductions as well as the indu cible accumulation of phytoalexins, suggesting that the A sojae beta -gluca n-induced transient cytosolic Ca2+ increase is not necessary for the elicit ation of H2O2 production but is very likely required for phytoalexin synthe sis (C) 2001 Federation of European Biochemical Societies. Published by Els evier Science B.V. All rights reserved.