Transcriptomics Reveals the Molecular Basis for Methyl Jasmonate to Promote the Synthesis of Monoterpenoids in Schizonepeta tenuifolia Briq.

Background: Methyl jasmonate has an important effect on the synthesis of plant secondary metabolites. Schizonepeta tenuifolia Briq. has a wide range of pharmacological effects and the secondary metabolites are dominated by monoterpenes (pulegone, menthone). Objective: It is essential to determine the changes in secondary metabolites in S. tenuifolia under methyl jasmonate treatment and to probe the molecular mechanism. This can improve the accumulation of secondary metabolites in the medicinal plant S. tenuifolia and enrich the information gene expression at different MeJA levels, which can help to elucidate the molecular mechanism of monoterpenoid synthesis in S. tenuifolia. Methods: In this study, we determined the changes in the content of monoterpenoids in S. tenuifolia under methyl jasmonate treatment. Meanwhile, we established a transcriptome database of S. tenuifolia under methyl jasmonate level using high-throughput sequencing. Results: A certain concentration of MeJA promoted the accumulation of monoterpenoids in S. tenuifolia. The transcriptome database of S. tenuifolia leaves under 0, 50, 100 and 250 μM MeJA treatment was established. We generated 88,373 unigenes with an N50 length of 2678 bp, of which 50,843 (57.53%) can be annotated in at least one database. Compared with the CK (0 μM) group, 12,557 (50 μM), 15,409 (100 μM) and 13,286 (250 μM) differentially expressed genes were identified. GO and KEGG enrichment analysis revealed that JA signal transduction and monoterpenoid synthesis were the two most significant enrichment pathways. The expression levels of related DEGs involved in JA signaling and monoterpenoid synthesis were significantly up-regulated by MeJA. In addition, our phenotypic and differentially expressed gene association analysis revealed that monoterpenoid biosynthesis in S. tenuifolia was more associated with genes involved in plant trichome branching, phytohormone signaling and transcriptional regulation. Conclusions: This study confirmed that methyl jasmonate significantly promoted monoterpenoid biosynthesis in S. tenuifolia. A large number of genes responding to methyl jasmonate were associated with JA signaling and monoterpenoid biosynthesis.