Involvement of cAMP signaling in elicitor-induced phytoalexin accumulation in Cupressus lusitanica cell cultures.

•  An increasing body of evidence on plant electrophysiology, biochemistry, and molecular biology shows that cAMP exists in higher plants and plays a role in several physiological processes by affecting potassium (K ) or calcium (Ca ) fluxes. Our study here reports that cAMP is involved in elicitor-induced accumulation of a phytoalexin, β-thujaplicin, in Cupressus lusitanica cell cultures. •  Treatment of C. lusitanica cultured cells with cAMP or its analogues stimulated β-thujaplicin accumulation. Cholera toxin and forskolin, activators of adenylyl cyclase, also stimulated β-thujaplicin accumulation. Enzyme immunoassay showed that after elicitor treatment, cAMP level in the elicited cells quickly increased to about three- to five-fold over the control. Cholera toxin and forskolin also stimulated cAMP accumulation in the absence of elicitor. •  However, K and Ca channel blockers inhibited the β-thujaplicin accumulation induced by cAMP analogues, suggesting that the cAMP-stimulated β-thujaplicin accumulation may involve Ca and K fluxes. Several ionophores mimicked cAMP induction of β-thujaplicin accumulation. •  Cross-talk between cAMP treatment and the ethylene signaling pathway was also observed to work in the cell cultures via Ca signaling. The study also indicates an involvement of protein kinase cascades in cAMP signaling processes, leading to both phytoalexin and ethylene production.