Artemisia annua mutant impaired in artemisinin synthesis demonstrates importance of nonenzymatic conversion in terpenoid metabolism

Czechowski, T., Larson, T. R., Catania, T. M., Harvey, D., Brown, G. D. and Graham, I. A. (2016) Artemisia annua mutant impaired in artemisinin synthesis demonstrates importance of nonenzymatic conversion in terpenoid metabolism. Proceedings of the National Academy of Sciences of the United States of America, 113 (52). pp. 15150-15155. ISSN 1091-6490 doi: 10.1073/pnas.1611567113

Abstract/Summary

Artemisinin, a sesquiterpene lactone produced by Artemisia annua glandular secretory trichomes, is the active ingredient in the most effective treatment for malaria currently available. We identified a mutation that disrupts the amorpha-4,11-diene C-12 oxidase (CYP71AV1) enzyme, responsible for a series of oxidation reactions in the artemisinin biosynthetic pathway. Detailed metabolic studies of cyp71av1-1 revealed that the consequence of blocking the artemisinin biosynthetic pathway is the redirection of sesquiterpene metabolism to a sesquiterpene epoxide, which we designate arteannuin X. This sesquiterpene approaches half the concentration observed for artemisinin in wild-type plants, demonstrating high-flux plasticity in A. annua glandular trichomes and their potential as factories for the production of novel alternate sesquiterpenes at commercially viable levels. Detailed metabolite profiling of leaf maturation time-series and precursor-feeding experiments revealed that nonenzymatic conversion steps are central to both artemisinin and arteannuin X biosynthesis. In particular, feeding studies using 13C-labeled dihydroartemisinic acid (DHAA) provided strong evidence that the final steps in the synthesis of artemisinin are nonenzymatic in vivo. Our findings also suggest that the specialized subapical cavity of glandular secretory trichomes functions as a location for both the chemical conversion and the storage of phytotoxic compounds, including artemisinin. We conclude that metabolic engineering to produce high yields of novel secondary compounds such as sesquiterpenes is feasible in complex glandular trichomes. Such systems offer advantages over single-cell microbial hosts for production of toxic natural products.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/68470
Item Type	Article
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
Publisher	National Academy of Sciences
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