Effect of salt stress on terpenoid biosynthesis in Salvia mirzayanii: from gene to metabolite

Salvia mirzayanii is a medicinal and aromatic plant with many pharmaceutical properties. The aims of this study were to isolate and characterise a specific gene involved in biosynthesis of major terpenoids produced by S. mirzayanii under increasing salinity stress, followed by investigation of photosynthetic responses under which yield of these terpenoids increased. Plants were grown in a greenhouse and harvested after 3 weeks’ exposure to different levels of salinity stress (25, 50, 75, and 100 mM NaCl). The isolation and expression analysis by RT-PCR of cineole synthase 1 gene (SmCin1), in response to 75 mM NaCl treatment, was investigated. Results showed that although the net photosynthesis and chlorophyll concentration decreased when salt stress severity increases, the amount of major terpenoids, α-terpinyl acetate, 1,8-cineole, and linalyl acetate increased. Expression analysis showed that SmCin1 transcript accumulated in leaves by approximately 11-fold during early hours of salinity treatment compared with non-treated (control) plants. The phylogenetic and sequence alignment analyses revealed that SmCin1 (GenBank accession no. KT438251.1) is closely aligned with other Salvia Cin1 genes in the GenBank (45–100%). These findings could be applied in economic cultivation, breeding programmes, and genetic engineering of S. mirzayanii to produce higher yields of terpenoids.