Elicitor-stimulated benzophenanthridine alkaloid biosynthesis in bloodroot suspension cultures is mediated by calcium

Abstract

Addition of an elicitor derived from the fungus Penicillium expansum Link (PE-elicitor) or the calcium ionophore A23187, to a suspension-cell culture of Sanguinaria canadensis induced the production of the benzophenanthridine alkaloids, sanguinarine and chelerythrine, in a dose-dependent manner. Pretreatment of the cells with the specific calcium chelatant EGTA (3 mM) or the calcium channel inhibitor verapamil (100 μM), for 1 hr prior to the addition of the PE-elicitor, decreased the accumulation of both sanguinarine and chelerythrine. Moreover, A23187-stimulated alkaloid accumulation was almost completely inhibited by pretreating the suspension cells with EGTA (3 mM) for 1 hr and this suppression was reversed by the readdition of calcium ions to the medium. Furthermore, addition of trifluoperazine (100 μM) to the suspension-cell cultures 1 hr before the PE-elicitor (35 μg Glc equ ml −1) treatment suppressed the accumulation of benzophenanthridine alkaloids by 51% as compared to suspension cells treated with PE-elicitor alone. These results demonstrate that an external source of calcium ions is required for elicitor-induced benzophenanthridine alkaloid accumulation and suggest that calcium and possibly calmodulin and/or protein kinase C may participate in a signal transduction system that mediates this process.