Elicitors in in Vitro Cultures

Induction of synthesis, accumulation, and release of secondary metabolites by elicitors is primarily a subject of phytopathology. The metabolites formed are plant-specific, in various plants structurally quite diverse, and generally show antimicrobial activity. They are referred to as phytoalexins. Isoflavonoids which occur in plants in response to elicitation by pathogens may be regarded as the model compounds of phytoalexins. Plant cell cultures can be employed to simulate the production of phytoalexins (Hahlbrock et al. 1988). Wolters and Eilert (1983) suggested to use plant cells cultured in vitro, specifically their formation of secondary metabolites upon elicitation for industrial exploitation. The results of subsequent experimentation in a number of laboratories vary from substantial enhancement of product formation to no measurable response, i.e. exposure of plant cells to elicitors did not increase the level of product accumulation over that obtained previously. As far as products resulting from elicitation of plant cell cultures furnished substantial yields of desirable compounds, elicitation in vitro has become a matter of much discussion. Focal points are (1) observations of product formation and industrial relevance, (2) the process of elicitation and aspects of genetic modification, and (3) re-elicitation.