Synergistic effect of UV-A and Methyl Jasmonate on the Biosynthesis of Thymol and Carvacrol Metabolites in Thymus

In thyme, thymol and carvacrol have attracted the attention of pharmacologists due to their various therapeutic properties such as anti-tumor activity. To date, a variety of treatments such as elicitors have been proposed to increase the content of thymol and carvacrol. This study was also conducted with the aim of evaluating the synergistic effect of UV-A ray and methyl jasmonate on the biosynthesis of thymol and carvacrol.

Thyme seeds were planted in plastic pots at a factorial experiment in time with a completely randomized design with three replications under greenhouse conditions. The five-leaf seedlings were separately and simultaneously irradiated with UV-A and sprayed with 0.1 mM methyl jasmonate. After 24 and 48 h of treatment, the expression levels of GTS, DXR, CYP180, and CYP178 genes were measured by Real-Time PCR and the metabolite levels were measured by HPLC.

The expression of GTS, DXR, CYP180, and CYP178 genes was affected by the synergistic impact of methyl jasmonate and UV-A. The transcript level of these genes increased significantly after 24 h of individual treatments and this increase was more in the combined treatment of hormone and radiation. However, the expression of these genes was linked with a significant decrease after 48 h of treatment. The increasing and decreasing trend of thymol and carvacrol content in the elicitor treatments was also in accordance with the expression of studied genes.

Our observations suggest that thyme uses synergistic signaling to increase its metabolite levels during the first 24 h of hormone and radiation treatments. And after that, other defense mechanisms are activated and then the level of secondary metabolites decreases.