STIMULATION OF ANTHRAQUINONE PRODUCTION IN RHUBARB TISSUE-CULTURE BY AN ETHYLENE-GENERATING REAGENT

The production of the anthraquinone derivatives chrysophanol and emodin in cultured rhubarb tissue was greatly stimulated by treatment of the cells with the ethylene-generating reagent 2-chloroethylphosphonic acid (2-CEPA). Addition of the calcium ionophore A23187 to the culture also enhanced the biosynthesis of these pigments. 2-CEPA-stimulated production of the anthraquinones was significantly inhibited in the presence of verapamil or LaCl3, two calcium influx inhibitors. Trifluoperadine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide, which are known to inhibit calmodulin-dependent processes, were also found to depress the production of these pigments. These results suggested that the stimulation of anthraquinone biosynthesis by rhubarb cells by ethylene is mediated by a transmembrane signalling system leading to calcium influx followed by activation of a calcium cascade in the cells.