Time-course analysis of the artemisinin biosynthesis, and expression of genes coding for artemisinin pathway enzymes, in response to exogenous salicylic and gibberellic acids

Artemisinin represents medicinally employed compound of Artemisia annua (L.) and is widely used against a num- ber of diseases. This study presents the effect of an exogenous application of salicylic acid (SA) and gibberellic acid (GA3) on the expression of genes coding for artemisinin pathway enzymes as well as on the biosynthesis of artemisinin. We found a temporary increase in artemisinin content in A. annua leaves 12 h after SA application. However, the transcript levels of all studied genes coding for artemisinin pathway enzymes decreased throughout the period studied and artemisinin content dropped down to an even lower level than in control plants at 168 h after treatment. In addition, artemisinin content increased, together with up-regulation of genes coding for enzymes of artemisinin biosynthesis pathway, owing to GA3 application. However, down-regulation of all investigated genes was also observed at 72 h after treatment, probably due to the negative feedback control. As can be seen, both SA and GAS exogenous applications can increase artemisinin accumulation in different ways. Because of a temporary increase in artemisinin content after SA or GA3 application, it is critical to determine the best harvesting time. Future research should focus on removing the negative feedback mechanism to achieve high- yield Artemisia plants.