Expression of artemisinin biosynthesis genes in eight Artemisia species at three developmental stages

In this study, the researchers have chosen eight species of Artemisia in order to find out their artemisinin content and also the expression levels of eight genes involved in the artemisinin biosynthetic pathway at three different developmental stages, i.e., vegetative, budding and flowering stages. Artemisinin was produced in all the species, albeit in various amounts (0.45-5.3 mg/g DW). In four species (Artemisia absinthium, Artemisia diffusa, Artemisia sieberi and Artemisia spicigeria), maximum level of artemisinin production was observed at the flowering stage, while in the other three species (Artemisia annua, Artemisia campestris and Artemisia vulgaris) artemisinin production reached its maximum level at the budding stage. However, Artemisia scoparia is the only species showing highest artemisinin content at the vegetative stage that was correlated with high density of glandular trichomes in leaf tissue. The higher amount of artemisinin, produced in A. annua, was mainly a result of higher expression of the amorpha-4,11-diene synthase (ADS) and artemisinic aldehyde Δ11(13) reductase (DBR2) genes. While, for A. absinthium an increased expression of alcohol dehydrogenase 1 (ALDH1) gene along with decreased expression of dihydroartemisinic aldehyde reductase (RED1) gene resulted in a desirable increase in artemisinin yield. The results of the study indicate that there is a relationship between increased expression of some genes and enhancement of artemisinin content. However, in order to validate the relationship, further enzymatic analysis needs to be performed.