Metabolic engineering of artemisinin biosynthesis in Artemisia annua L

Artemisinin, a sesquiterpene lactone isolated from the Chinese medicinal plant Artemisia annua L., is an effective antimalarial agent, especially for multi-drug resistant and cerebral malaria. To date, A. annua is still the only commercial source of artemisinin. The low concentration of artemisinin in A. annua, ranging from 0.01 to 0.8% of the plant dry weight, makes artemisinin relatively expensive and difficult to meet the demand of over 100 million courses of artemisinin-based combinational therapies per year. Since the chemical synthesis of artemisinin is not commercially feasible at present, another promising approach to reduce the price of artemisinin-based antimalarial drugs is metabolic engineering of the plant to obtain a higher content of artemisinin in transgenic plants. In the past decade, we have established an Agrobacterium-mediated transformation system of A. annua, and have successfully transferred a number of genes related to artemisinin biosynthesis into the plant. The various aspects of these efforts are discussed in this review.