Interaction of methyl jasmonate, wounding and fungal elicitation during sesquiterpene induction in Hyoscyamus muticus in root cultures

The ability of methyl jasmonate (MeJa) to induce sesquiterpene production in root cultures of Hyoscyamus muticus has been studied. Although MeJa alone could not induce sesquiterpene in unwounded culture, MeJa added in the presence of wounding displayed a dose-dependent response, saturating at 50 μM. The ability to respond to MeJa declined with an increase in time between MeJa contact and wounding; however, responsiveness could be recovered by re-wounding of tissue prior to MeJa contact, suggesting that additional signaling related to wounding is required for sesquiterpene pathway induction. The saturation level of sesquiterpene induction with fungal elicitor was four times higher than the saturation level achieved by MeJa, with clear differences in sesquiterpene composition. Fungal elicitation results in a higher level of lubimin and a lower level of solavetivone production; whereas, methyl jasmonate induces predominantly solavetivone and little or no lubimin production. This suggests that fungal elicitation induces enzymes further down the sesquiterpene pathway which are not affected by MeJa. The induction of roots in contact with subsaturated levels of elicitor can be enhanced to saturation production levels by the addition of small amounts of MeJa (5-10 μmoles/l). In these studies, MeJa was consistently found to favor the earlier metabolite (solavetivone), while fungal elicitation promoted conversion to subsequent metabolites in the pathway (lubimin). The interactive role of MeJa in signal transduction for secondary metabolic production is discussed.