methyl-jasmonate and mastoparan

When growth-phase cell suspension cultures of Capsicum annuum were treated with cellulase-elicitor preparation at 3 microg/ml, the level of capsidiol was transiently increased in the culture media rather than in the cells reaching its maximum approx 24 h after treatment. With methyl jasmonate it took 18 h. Elicitor treatment doubled phospholiphase A(2) (PLA(2)) activity but simultaneous treatment with aristolochic acid, a PLA(2) inhibitor, inhibited sesquiterpenoid accumulation as well as PLA(2) activity. Mastoparan, a G protein activator, treatment also increased PLA(2) activity and capsidiol production. Taken together, the present study shows that induction of capsidiol production in the C. annuum is mediated by PLA(2) activation.

Topics: Acetates; Aristolochic Acids; Capsicum; Cells, Cultured; Cellulase; Chromatography, Gas; Cyclopentanes; Intercellular Signaling Peptides and Proteins; Oxylipins; Peptides; Phospholipase A2 Inhibitors; Phospholipases A2; Sesquiterpenes; Time Factors; Wasp Venoms

The biosynthesis of a phytoalexin, beta-thujaplicin, in Cupressus lusitanica cell cultures can be stimulated by a yeast elicitor, H(2)O(2), or methyl jasmonate. Lipoxygenase activity was also stimulated by these treatments, suggesting that the oxidative burst and jasmonate pathway may mediate the elicitor-induced accumulation of beta-thujaplicin. The elicitor signalling pathway involved in beta-thujaplicin induction was further investigated using pharmacological and biochemical approaches. Treatment of the cells with calcium ionophore A23187 alone stimulated the production of beta-thujaplicin. A23187 also enhanced the elicitor-induced production of beta-thujaplicin. EGTA, LaCl(3), and verapamil pretreatments partially blocked A23187- or yeast elicitor-induced accumulation of beta-thujaplicin. These results suggest that Ca(2+) influx is required for elicitor-induced production of beta-thujaplicin. Treatment of cell cultures with mastoparan, melittin or cholera toxin alone or in combination with the elicitor stimulated the production of beta-thujaplicin or enhanced the elicitor-induced production of beta-thujaplicin. The G-protein inhibitor suramin inhibited the elicitor-induced production of beta-thujaplicin, suggesting that receptor-coupled G-proteins are likely to be involved in the elicitor-induced biosynthesis of beta-thujaplicin. Indeed, both GTP-binding activity and GTPase activity of the plasma membrane were stimulated by elicitor, and suramin and cholera toxin affected G-protein activities. In addition, all inhibitors of G-proteins and Ca(2+) flux suppressed elicitor-induced increases in lipoxygenase activity whereas activators of G-proteins and the Ca(2+) signalling pathway increased lipoxygenase activity. These observations suggest that Ca(2+) and G-proteins may mediate elicitor signals to the jasmonate pathway, and the jasmonate signalling pathway may then lead to the production of beta-thujaplicin.

Topics: Acetates; Calcimycin; Calcium; Cells, Cultured; Cholera Toxin; Cupressus; Cyclopentanes; Egtazic Acid; Fungi; GTP Phosphohydrolases; GTP-Binding Proteins; Hydrogen Peroxide; Intercellular Signaling Peptides and Proteins; Lanthanum; Lipoxygenase; Monoterpenes; Oxylipins; Peptides; Plant Growth Regulators; Signal Transduction; Suramin; Tropolone; Verapamil; Wasp Venoms