Compact callus cluster suspension cultures of Catharanthus roseus with enhanced indole alkaloid biosynthesis

Compact callus clusters showing a certain level of cellular or tissue differentiation were established from Catharanthus roseus stem and leaf explants in a modified MS liquid induction medium supplemented with 5.37 muM alpha -naphthaleneacetic acid and 4.65 muM kinetin. In the induction medium most leaf explants developed into friable half-closed hollow callus clusters, whereas in the same medium containing 2,4-dichlorophenoxyacetic acid instead of alpha -naphthaleneacetic acid, most leaf explants were induced to form dispersed cell suspension cultures. Characteristics of these different types of suspension cultures were compared, and the results showed that the compact callus clusters could synthesize indole alkaloids 1.9- and 2.4-fold higher than the half-closed hollow callus clusters and dispersed cell cultures, respectively. The degree of compaction expressed by the ratio of fresh weight to dry weight of these suspension cultures was correlated to indole alkaloid production. Our studies also postulated that the level of cellular/tissue differentiation might be responsible for these different alkaloid synthesis capabilities. Sucrose regime affected some properties (the size, degree of compaction, differentiation level) of the compact callus cluster cultures and therefore influenced alkaloid production.