The antimalarial substance artemisinin is a terpene produced in small amounts in the plant Artemisia annua L.  Because of the low yield, artemisinin-based drugs are expensive and therefore not available for many living in poor areas in the world where malaria claims up to a million lives each year. To increase artemisinin yield in A. annua, a lot of research needs to be done to understand the mechanisms for how the plant synthesizes this terpene compound artemisinin.

In this work, the gene expression of several genes in A. annua involved in terpene production have been studied, especially those in the biosynthetic pathway of artemisinin. The gene expression has been measured and compared in different tissues of the plant. Further, the artemisinin production in the plant takes place in small 10-cellular outgrowths on the surface of the plant, called glandular trichomes. The gene expression in glandular trichomes has been examined by comparing untreated stem with stem where trichomes have been removed mechanically.

All enzymes except one in the artemisinin pathway showed highest expression in young leaves and flower buds, both tissues with high glandular trichome count, and less or no expression in roots, which lack glandular trichomes. The artemisinin pathway enzyme artemisinic aldehyde reductase surprisingly showed similar expression in all tissues. Old leaves highly expressed the enzyme 8-epi-cedrol synthase that competes for substrates used in artemisinin biosynthesis. Young leaves on the other hand highly expressed another competing enzyme, germacrene A synthase.