Activation of Ethylene Production in Acer pseudoplatanus L.Cultured Cells by Fusicoccin

Ethylene production by suspension cultures of sycamore cells (Acer pseudoplatanus L.) is regulated by2,4-Dichlorophenoxyacetic acid (2,4-D) and by the age of the culture. It is not stimulated by applied 1-aminocyclopropane-1-carboxylic acid (ACC). Fusicoccin enhanced the rate of ethylene formation, in addition to the stimulation of proton extrusion. The effects of fusicoccin and 2,4-D were additive. The fusicoccin dependent ethylene production was not modified by addition of ACC and, as the basal production, was strongly inhibited by aminoethoxyvinylglycine (AVG) and by cobaltous ions. Moreover it occurred without a significant increase of 1-aminocyclopropane-1-carboxylic acid per cell. The stimulation by fusicoccin could be already noticed at the first hour of treatment and reached its maximum at the third hour. The effect of fusicoccin was not prevented by cycloheximide (CHE). ≪In vitro≫ measures of ACC oxidase activity of extracts from control or fusicoccin treated cells indicated that the level of this enzyme in the cells was not changed. The data suggest that in our cultures ACC oxidase is the limiting step of ethylene production and that fusicoccin increases this activity without ≪de novo≫ synthesis of ACC oxidase.