Cytokinins and ethylene stimulate indole alkaloid accumulation in cell suspension cultures of Catharanthus roseus by two distinct mechanisms

The interactions between cytokinins and ethylene on alkaloid accumulation in a periwinkle cell line have been examined. It was found that (a) either exogenously-applied cytokinins or ethylene (the latter through ethephon degradation) greatly enhanced ajmalicine accumulation in cells subcultured in a 2,4-dichlorophenoxyacetic acid-free medium; (b) the enhancing effect of cytokinin was not mediated by enhancement of endogenous ethylene production contrary to what is found in some plant models; (c) the responses to exogenous cytokinin and ethylene were additive and showed a different pattern of expression. It may be concluded that cytokinin and ethylene can up-regulate the alkaloid production in a periwinkle cells through independent pathways when added exogenously to the cultures.