Stimulation of calcium signal transduction results in enhancement of production of scopadulcic acid B by methyl jasmonate in the cultured tissues of Scoparia dulcis

Signal transduction events which are involved in methyl jasmonate (MeJA)-enhanced production of the tetracyclic diterpene, scopadulcic acid B (SDB), were investigated in leaf organ cultures of Scoparia dulcis. Pretreatment of leaf organ cultures with Ca²⁺-channel blocker, verapamil, resulted in a dose-dependent inhibition of MeJA enhanced SDB production. Treatments with Ca²⁺ ionophore, A23187, stimulated SDB production in the absence of MeJA. In addition, preincubation of the leaf organ cultures with calmodulin (CaM) antagonist, trifluoperazine (TFP), diminished MeJA enhanced SDB production. MeJA-enhanced production of SDB was suppressed by addition of protein kinase inhibitors such as staurosporine and 2,6-diamino-N-([1-(1- oxotridecyl)-2-piperdinyl]methyl)hexanamide (NPC-15437). An activator of protein kinase C, 1-oleoyl-2-acetyl-sn-glycerol (OAG), stimulated this production in the absence of MeJA. These results indicate that Ca²⁺ and CaM mediates signaling events leading to enhancement of SDB production upon MeJA treatment. It was also suggested that phosphorylation of protein by protein kinases might be involved in this signal pathway.