Comparison of The Expression Level of Two Sesquiterpene Cyclases Genes in The Transformed Hairy Roots of Artemisia annua L. Plant

Abstract

As early as 500 BC, ancient Chinese scripts reported the use of the annual herb, Artemisia annua, for treatment of “fever” (Klayman, 1985). Much later, Qinghaosu, artemisinin, a sesquiterpene lactone, was isolated in pure form from the aerial parts of Artemisia annua L. (annual wormwood) plants, and its structure was determined in 1979 (Klayman, 1985). Artemisinin is currently the best therapeutic against both drugresistant and cerebral malaria-causing strains of Plasmodium falciparum. It has since become popular throughout Southeast Asia and Africa, where malaria has become resistant to nearly all anti-malarial drugs, including chloroquine, quinine, mefloquine, and Fansidar (Newton et al., 1999).
Artemisinin is an important thera- peutic that, along with its derivatives, is a proven treatment for a number of diseases besides malaria (Dhingra et al., 2000), other parasites like schistosomiasis (Utzinger et al., 2001; Borrmann et al., 2001), and more recently cancer and Hepatitis B (Romero et al., 2005). Artemisinin has also been shown to be effective against a variety of cancer cell lines including breast cancer, human leukemia, colon, and small-cell lung carcinomas (Efferth et al., 2001; Singh and Lai 2001). Furthermore, artemisinin may be especially effective in treating drug resistant cancers (Sadava et al., 2002; Efferth et al., 2002). However, the drug is in short supply as its complex structure still requires that it be extracted from plants. Although others are working on a synthetic trioxolane (Vennerstrom et al., 2004) and bacterial produced artemis- inin precursors (Martin et al., 2003) that may replace artemisinin as an inexpensive therapeutic, A. annua plants are still the only current source of the drug.
In the whole plant artemisinin has been reported to accumulate in leaves, small green stems, buds, flowers and seeds (Liersch et al., 1986; Ferreira et al., 1995) with highest levels in leaves and flowers. Neither artemisinin nor its pre- cursors, however, were detected in roots (Charles et al., 1990). Artemisinin content in full bloom flowers was 4-5 times higher than in leaves (Ferreira et al., 1995). Both leaves and flowers of A. annua have trichomes. Duke et al. (1994) showed that artemisinin is sequestered in the glandular trichomes of A. annua, and that glandless types produce no artemisinin (Ferreira et al., 1995). Some researchers reported that artemisinin content is highest just prior to flowering (Liersch et al., 1986; Woerden- bag et al., 1994) while others found an artemisinin peak at full flowering stage (Morales et al., 1993, Pras et al., 1991; Singh et al., 1988).