Regulation of Product Synthesis in Cell Cultures ofCatharanthus roseus. III. Alkaloid Metabolism in Cultured Leaf Tissue and Primary Callus1

Cultured leaf discs of Catharanthus roseus produced visible callus under a variety of cultural conditions within 10 to 15 days. A peak of respiratory activity typical of rapidly growing callus was observed after 10-20 days culture. Photosynthesis was inactivated on transferring leaf tissue into culture within 5 days. During this period the two main leaf alkaloids, catharanthine and vindoline, were rapidly metabolised and were not found in primary callus or in the original leaf tissue after 40 days culture. The alkaloids serpentine and ajmalicine accumulated in leaf tissue but predominantly in callus, during the callus induction and growth period. Serpentine was the major alkaloid accumulated in the light and ajmalicine in the dark. Maximal alkaloid accumulation was found with the production media devised by Zenk but sustained callus growth did not occur. Cultures which accumulated high levels of serpentine over repeated subcultures were derived on other media, but these cultures did not contain catharanthine or vindoline.