In this paper, parts of the signaling cascade involved in defense against pathogens and elicitors were activated as a means of enhancing secondary metabolite accumulation in plant cell cultures. Instead of adding pathogens to activate the entire signaling cascade, we focused on the role of two specific signaling molecules in this signal transduction pathway, methyl jasmonate (MJ) and Ca²⁺, and their effect on the accumulation of terpenoid indole alkaloids (TIAs) from Catharanthus roseus cell cultures.

The effectiveness of jasmonates on enhancing TIA production depended on the timing of induction. In our C. roseus suspensions, the optimum culture stage and the corresponding optimum dosage for enhancing the production of a marker TIA, ajmalicine, with jasmonate was during rapid growth (i.e. day 6) with 10-100 µM methyl jasmonate (MJ). The interaction between Ca²⁺ and MJ in modulating TIA production was also explored by culturing cells in nine combinations of CaCl₂ (3, 23, and 43 mM) and MJ (0, 10, and 100 µM) or by treating cells with Ca²⁺ chelator EGTA or Ca²⁺ channel blocker verapamil. Although gene expression was reported to increase with Ca²⁺ and MJ in the literature, ajmalicine production in our MJ-induced C. roseus was not amplified. However, Ca²⁺ was necessary for MJ-induced ajmalicine production in C. roseus cultures. To further increase production, the enzymatic bottlenecks to TIA production from these MJ-induced C. roseus cultures were investigated through precursor feeding, pointing to specific bottlenecks to be explored further.