Effects of salinity stress on the growth, physiological parameters and genes expression of thymol and carvacrol in Thymus daenensis

Thymus daenensis Celak. is a perennial plant belonging to the family Lamiaceae that contains various monoterpenes such as thymol and carvacrol. In order to investigate the effect of salinity stress on growth, the content of thymol and carvacrol compounds and the expression of genes involved in the biosynthetic pathway of these compounds, an experiment was conducted in the research greenhouse in the form of a randomized complete block design with three replications. The results showed that salinity stress had a significant effect on the studied traits at a 1% probability level. Salinity stress at the level of 150 mM NaCl caused a significant reduction in plant height, fresh and dry weight and increasing of total phenol, flavonoids contents, PAL enzyme activity. The content of thymol and carvacrol in salinity stress significantly increased. Study of the genes expression involved in the biosynthesis of these compounds indicated that the genes expression of DXR, terpenes synthase, α-terpinene synthase and ү-terpinene synthase increased in comparison to control. These increments of increase in gene expression of DXR compared with other studied genes were much higher. Therefore, it can be concluded that the increase of secondary metabolites in Thymus daenensis, thymol and carvacrol, in salinity stress conditions due to increased expression of DXR key gene. It is expected to increase these metabolites in the future with its engineering.