Enhancement of artemisinin content and relative expression of genes of artemisinin biosynthesis in Artemisia annua by exogenous MeJA treatment

Methyl jasmonate (MeJA) is one of the most potent elicitors that can induce over accumulation of many natural products including artemisinin in plants. The 12 known genes (HMGR, DXS, DXR, HDS, HDR, FPS, ADS, CYP71AV1, DBR2, ALDH1, ORA and ERF1) of terpene metabolism in Artemisia annua were dynamically analyzed at the transcriptional levels in the treatment of MeJA from 0 to 48 h. HMGR (MVA pathway) showed higher expression level when the plants were treated with MeJA from 1 to 9 h and had the highest expression level at 3 h MeJA treatment. The expression levels of DXS and DXR (MEP pathway) reached the peak at 9 h. The last two genes of the MEP pathway, such as HDS and HDR, had the highest expression levels at 24 h. The expression of FPS increased significantly in the treatment of MeJA from 1 to 48 h, and the highest expression level appeared at 24 and 48 h after the MeJA treatment. Four genes in artemisinin-specific biosynthetic pathway including ADS, CYP71AV1, DBR2 and ALDH1 had higher expression levels in the treatment of MeJA from 1 to 48 h. The expression levels of two transcription factors such as ORA and ERF1 were also enhanced. The contents of artemisinin in the plants treated with MeJA for 24 and 48 h were respectively 0.971 and 0.973 mg/g DW, about 1.16-fold of the control (0.809 mg/g DW). Taken together, these results suggested that MeJA induced artemisinin biosynthesis by up-regulating the expression of the genes involved in artemisinin biosynthesis and the transcription factor.