Abstract

Lignans are dimers of phenylpropanoid units. The most important lignan for human health is podophyllotoxin (PTOX), from which semisynthetic derivates like Etopophos® are used in cancer therapy. Up to now PTOX is extracted from roots and rhizomes of Podophyllum hexandrum which is now an endangered species due to over collection. Since only a few steps in the biosynthesis of PTOX are known up to now, we set out to clone genes involved in PTOX biosynthesis by using molecular biological approaches based on differential PTOX accumulation. To this end, we first established that 50µM of the synthetic elicitor coronalon (CR) [1.] are sufficient, but 700µM methyl-jasmonate (MJ) are necessary to give a fourfold induction of PTOX accumulation up to 8mg/g dry weight and a sixfold induction in 6-methoxypodophyllotoxin (6MPTOX) accumulation reaching 0.6mg/g dry weight in a cell suspension culture of Linum album grown in 300ml erlenmeyer flasks. It has to be mentioned that CR was the better elicitor for PTOX biosynthesis whereas application of MJ gave higher enhancement of 6MPTOX biosynthesis. This fact was confirmed when we followed the specific enzymatic activities of four selected enzymes involved in the biosynthesis of PTOX and/or 6MPTOX over a cultivation period of 7 days after elicitation with MJ. The cell culture of L. album accumulated 3.5mg/g dry weight PTOX and 0.16mg/g dry weight 6MPTOX after elicitation with 700µM MJ when it was grown in a 30 L stirred tank bioreactor.

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