Contribution à l'étude de la régulation génique de la synthèse des alcaloïdes indoliques chez la pervenche tropicale

TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Clonage et caractérisation de gènes corrélés à la biosynthèse des alcaloïdes indoliques monoterpéniques de Catharanthus roseus

TOURS-BU Sciences Pharmacie (372612104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Cytokinins and ethylene stimulate indole alkaloid accumulation in cell suspension cultures of Catharanthus roseus by two distinct mechanisms

peer reviewedThe interactions between cytokinins and ethylene on alkaloid accumulation in a periwinkle cell line have been examined. It was found that (a) either exogenously-applied cytokinins or ethylene (the latter through ethephon degradation) greatly enhanced ajmalicine accumulation in cells subcultured in a 2,4-dichlorophenoxyacetic acid-free medium; (b) the enhancing effect of cytokinin was not mediated by enhancement of endogenous ethylene production contrary to what is found in some plant models, (c) the responses to exogenous cytokinin and ethylene were additive and showed a different pattern of expression. It may be concluded that cytokinin and ethylene can up-regulate the alkaloid production in a periwinkle cells through independent pathways when added exogenously to the cultures. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved

Cytokinin modulates catalase activity and coumarin accumulation in in vitro cultures of tobacco

Cytokinins (CKs) represent an important class of phytohormones particularly known for their antisenescence properties that might be regulated through an effect on the oxidative metabolism. In the present work, we demonstrate the effect of CKs on catalase activity in tobacco cultivated in vitro. The catalase activity observed in suspension-cultured cells decreased slightly during the first hour of CK treatment and increased thereafter to double the level detected in untreated cells. In contrast to these results, catalase activity was inhibited in shoot cultures in which the endogenous levels of CK were elevated by the introduction of the isopentenyltransferase gene or by an exogenous feeding of CK to the cultures. Interestingly, this catalase inhibition correlated with an accumulation of scopolin, an inducible coumarin. Taken together, our results show that CK modulates (directly or undirectly) catalase activity. The inverse relationship that was always found between scopolin accumulation and catalase activity is discussed in terms of vitrification and habituation