Comparative transcriptome analysis to identify putative genes involved in carvacrol biosynthesis pathway in two species of Satureja, endemic medicinal herbs of Iran

Satureja is rich in phenolic monoterpenoids, mainly carvacrol, that is of interest due to diverse biological activities including antifungal and antibacterial. However, limited information is available regarding the molecular mechanisms underlying carvacrol biosynthesis and its regulation for this wonderful medicinal herb. To identify the putative genes involved in carvacrol and other monoterpene biosynthesis pathway, we generated a reference transcriptome in two endemic Satureja species of Iran, containing different yields (Satureja khuzistanica and Satureja rechingeri). Cross-species differential expression analysis was conducted between two species of Satureja. 210 and 186 transcripts related to terpenoid backbone biosynthesis were identified for S. khuzistanica and S. rechingeri, respectively. 29 differentially expressed genes (DEGs) involved in terpenoid biosynthesis were identified, and these DEGs were significantly enriched in monoterpenoid biosynthesis, diterpenoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, carotenoid biosynthesis and ubiquinone and other terpenoid-quinone biosynthesis pathways. Expression patterns of S. khuzistanica and S. rechingeri transcripts involved in the terpenoid biosynthetic pathway were evaluated. In addition, we identified 19 differentially expressed transcription factors (such as MYC4, bHLH, and ARF18) that may control terpenoid biosynthesis. We confirmed the altered expression levels of DEGs that encode carvacrol biosynthetic enzymes using quantitative real-time PCR (qRT-PCR). This study is the first report on de novo assembly and transcriptome data analysis in Satureja which could be useful for an understanding of the main constituents of Satureja essential oil and future research in this genus.

Impacts of foliar exposure to multi-walled carbon nanotubes on physiological and molecular traits of Salvia verticillata L., as a medicinal plant

Owing to the growing applications of the multi-walled carbon nanotubes (MWCNTs) in the communications and energy industries, they have attracted increasing attention for their effects on the environment and plants. Therefore, we investigated the impact of foliar exposure to MWCNTs on the oxidative stress responses in the Salvia verticillata as a medicinal plant. Furthermore, we evaluated the possible correlations between gene expression and activity of the key enzymes in the phenolic acids biosynthesis pathways and their accumulation in the treated leaves. The leaves of two-month-old plants were sprayed with different concentrations (0-1000 mg L^-1) of MWCNTs. Raman's data and Transmission Electron Microscopy images have confirmed the absorption of MWCNTs via epidermal cells layer into the parenchymal cells of the exposed leaves. The results showed that exposure to MWCNTs led to a decrease in the photosynthetic pigments and increases in the oxidative stress indices (enzymatic and non-enzymatic antioxidants) in the leaves with a dose-dependent manner. The content of rosmarinic acid as a main phenolic acid was increased in the MWCNTs-exposed leaves to 50 and 1000 mg L^-1, nearly four times relative to the control. Unlike with other examined enzymes, a positive correlation was deduced between the activity and gene expression patterns of the rosmarinic acid synthase with the rosmarinic acid accumulation in the treatments. Overall, MWCNTs at the low concentrations could promote the production of the pharmaceutical metabolites by the changes in the ROS generation. However, at the higher concentrations, MWCNTs were toxic and induced the oxidative damages in S. verticillata.