The effects of water deficit stress and chitosan on cineole synthase gene expression and 1,8-cineole content in sage (Salvia officinalis)

Common sage (Salvia officinalis) is one of the most important medicinal and aromatic plants and possesses anticancer, antioxidant and antimicrobial properties. One of the essential oil components of the sage plant is monoterpene, 1,8-cineole, that is responsible for some of these effects. The effect of foliar application of chitosan (control, 0.0, 0.25 and 0.50 g/L) under different levels of water deficit (FC = 60, 75 and 100%) were investigated on the expression level of cineole synthase gene in the roots and accumulation of 1,8-cineole content in the leaves of the sage plants. The experiment was conducted as factorial based on completely randomized design with three replications. The level of gene expression was determined by real time PCR in plant roots and the 1,8-cineole content was identified by gas chromatography/mass spectrometry in leaves. Results indicated that the expression of studied gene and 1,8-cineole content were strongly up-regulated with water deficit. Furthermore, foliar application of chitosan (specially in 0.5 g/L) effectively up-regulated the cineole synthase gene expression in roots and 1,8-cineole content in the shoots. Overall, water deficit stress was more effective than chitosan in the up regulation of cineole synthase gene and 1,8-cineole synthase content. The maximum level of cineole synthase gene expression and 1,8-cineole content were observed in mild drought stress and 0.5 g/L chitosan condition. Slight water deficit stress had no effect on gene expression but the final product was increased in shoots. For the first time, our results indicated that water deficit stress and chitosan could increase cineole synthase gene expression in the roots of common sage. Therefore, chitosan along with water deficit probably increase 1,8-cineole content in shoots, in part, through increasing the expression level of 1,8-cineole synthase gene in roots.