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

Abstract

Summary• 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 2+ ) 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 threeto five-fold over the control. Cholera toxin and forskolin also stimulated cAMP accumulation in the absence of elicitor.• However, K + and Ca 2+ channel blockers inhibited the β -thujaplicin accumulation induced by cAMP analogues, suggesting that the cAMP-stimulated β -thujaplicin accumulation may involve Ca 2+ 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 2+ signaling. The study also indicates an involvement of protein kinase cascades in cAMP signaling processes, leading to both phytoalexin and ethylene production.

Cyclic GMP stimulates flower induction of Pharbitis nil via its influence on cGMP regulated protein kinase

“…PKV also has a putative sequence for nuclear targeting of proteins, which may target PKV to the nucleus. Interestingly, the promoter region of the PKV gene contains a G-box element that appears to function in the regulation of genes by developmental stimuli such as abscisic acid, pathogens and light, all responses in which cyclic nucleotides have been implicated (Liu et al 2002;Zhao et al 2004).…”

Molecular aspects of the early stages of elicitation of secondary metabolites in plants

“…In spite of incomplete characterization, the adenylyl cyclase/ cAMP/PKA pathway has been implicated in the elicitation process in Cupressus lusitanica and Arabidopsis [120,125]. However, pharmacological evidences have shown that the AC/ cAMP/PKA cascade does not contribute significantly to the elicitation mechanism triggered by chitosan in R. tinctorum [14].…”

“…For example, cAMP concentrations in plants are generally lower than in animals and the application of standard methods of detection can be unsuccessful [116]. Nevertheless, cAMP levels have been shown to augment in response to elicitor treatment and mediate the stimulation of phytoalexin biosynthesis in several species, such as carrot [117], lucerne [118], French bean [119] and Mexican cypress cell cultures [120].…”

Involvement of G‐proteins in chitosan‐induced Anthraquinone synthesis in Rubia tinctorum

“…Elicitors are known to activate different mechanisms related to the production of second messengers (Van der Luit et al 2000, Zhao et al 2004, thereby modulating genes that encode for various enzymes of biosynthetic pathways, thus inducing secondary metabolism. The polysaccharide chitosan has been widely used as elicitor (Darvill and Albersheim 1984, Doares et al 1995, Jin et al 1999, Kneer et al 1999.…”