Artemisinin and absinthin production in response to exogenous methyl jasmonate and chilling in Artemisia absinthium L. in vitro propagated plantlets

Sesquiterpene lactones with diverse biological activities are predominant secondary metabolites in the Asteraceae family. Artemisinin is the best-known sesquiterpene lactone in the genus Artemisia which, has proved to have antimalarial and anticancer activities. In addition to artemisinin, Artemisia absinthium L. produces absinthin as the main bitter sesquiterpene lactone. Here, the effects of exogenous methyl jasmonate (MJ) on cold stress responses of A. absinthium in vitro propagated plantlets in terms of physiological responses and secondary metabolites production have been investigated. Two-month-old in vitro germinated A. absinthium plantlets were exposed to 4 and 10 °C temperatures with and without MJ (25 μM) during 0, 8, 24, and 48 h time courses. Artemisinin and absinthin contents have been measured by HPLC and the transcript levels of sesquiterpene lactones biosynthetic genes, farnesyl pyrophosphate synthase (FPPS), and germacrene A synthase (GAS), as well as the MYB4 transcription factor were estimated by real-time qRT-PCR in treated plantlets. Results showed an increase in the levels of hydrogen peroxide (H₂O₂), indicating oxidative stress. Along with this, the activity of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POX) was elevated. Additionally, the levels of glycine betaine (GB), a compatible solute, were also increased. Significant positive correlations were observed between FPPS expression and the expression levels of MYB4 and GAS. However, no direct correlation was found between the expression levels of MYB4 and GAS. Overall, exogenous MJ reduced the adverse effects of cold stress on A. absinthium plantlets.