Involvement of calcium in ACC-oxidase activity from Cicer arietinum seed embryonic axes

Both in vivo and in vitro ACC-oxidase activities as well as ethylene produc tion from embryonic axes of chickpea seeds were strongly inhibited by EGTA, a selective extracellular Ca2+ ion chelator, indicating that the influx of Ca2+ is important for enzymatic activity. EGTA inhibition was restored by exogenous Ca2+. Treatments of embryonic axes with either Verapamil and LaCl 3 (both Ca2+ channel blockers) or TMB-8 (an intracellular Ca2+ antagonist) provoked an inhibition of both ACC-oxidase activity and ethylene production . These results suggest an involvement of calcium fluxes and intracellular calcium levels in the activity of the last step of the ethylene biosyntheti c pathway, which is, in turn, intimately correlated with germination of Cic er arietinum seeds. (C) 1998 Elsevier Science Ltd. All rights reserved.