MODULATION OF THE ELICITATION RESPONSE IN CULTURED FRENCH BEAN CELLS AND ITS IMPLICATION FOR THE MECHANISM OF SIGNAL TRANSDUCTION

A range of modulators have been used to investigate signal transduction involved in the response of suspension cultured cells of French bean to an elicitor preparation from the fungal pathogen Colletotrichum lindemuthianum. Elicitor action was effectively determined by the induction of phenylalanine ammonia-lyase (PAL) protein and activity. Three types of modulators were used. One group that potentially directly affected calcium mobilization and action had with the exception of caffeine and procaine no consistent effect on elicitor action. A number of ionophores and compounds that affect membrane ion transport were tested and the most effective was found to be monensin. Further studies showed that the inhibition of elicitation by monensin was more likely to be mediated by inhibition of uptake of elicitor than perturbation of ion transport. A third group of modulators were characterized by their ability in animal systems to interact with G proteins. A variety of effects were observed which were consistent with putative G protein involvement as a component of elicitor-induced signal transduction. Modulation of the induction of the synthesis of PAL protein and of PAL activity were both observed. Overall, the results were consistent with elicitor action being potentiated through multicomponent transduction pathways.