BIOSYNTHESIS OF TRITERPENOIDS IN CULTURED-CELLS, AND REGENERATED AND WILD PLANT ORGANS OF TARAXACUM-OFFICINALE

Undifferentiated cultured cells of Taraxacum officinale produced oleanolic and ursolic acids as major triterpenoids in addition to triterpenols composed mainly of alpha- and beta-amyrins. Regenerated and wild plants contained additional triterpenols, i.e. taraxasterol and lupeol, but negligible quantities of triterpene acids. [2-C-14]Mevalonic acid was fed to callus cells, wild plant organs, and shoot and root segments of plants redifferentiated from callus. After 48 hr incubation, triterpenols, phytosterols and triterpene acids were equally labelled in callus cultures; in contrast, triterpene acids were strongly labelled in the differentiated tissues. The incorporation of radioactivity into alpha- and beta-amyrins was highest in the callus where taraxasterol and lupeol were not labelled substantially; the latter were labelled in differentiated organs, agreeing with the accumulation patterns. A time course experiment with shoot segments showed a different production pattern of cycloartane triterpenes from other classes of triterpenoids. The results are discussed in relation to organ-specific biosynthesis of specific triterpenoids.