TRITERPENOID BIOSYNTHESIS IN THE ETIOLATED SEEDLING OF EUPHORBIA-LATHYRIS L DEVELOPMENTAL-CHANGES AND THE REGULATION OF LOCAL TRITERPENOID PRODUCTION

Intact seedlings of Euphorbia lathyris were used to measure the daily production of sterols, latex triterpenols and wax triterpene ketones, and to estimate the participation of sucrose and threonine in the synthesis of these lipids. In the early stage of seedling development, 3-4 days after seed imbibition (DAI), the biosynthesis of these triterpenoids is limited by enzymatic production capacity. From 5 DAI onwards, the triterpenoid production seemed to be restricted by the availability of sugars. Threonine played only a marginal role in the synthesis of triterpenoids. From 5-8 DAI, most of the triterpenoids are synthesized directly from sucrose taken up from the endosperm by the cotyledons. From 8-12 DAI, sugars from the hypocotyl and root became another source of carbon for triterpenoid synthesis. In 9-day-old seedlings, the production of latex triterpenols and triterpene ketones was most prominent in the rapidly elongating parts of the hypocotyl. The activity of sterol synthesis was most pronounced in the root tip.