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Background: Clinopodium gracile (Benth.) Matsum (C. gracile) is an annual herb with pharmacological properties effective in the treatment of various diseases, including hepatic carcinoma. Triterpenoid saponins are crucial bioactive compounds in C. gracile. However, the molecular understanding of the triterpenoid saponin biosynthesis pathway remains unclear. Results: In this study, we performed RNA sequencing (RNA-Seq) analysis of the flowers, leaves, roots, and stems of C. gracile plants using the BGISEQ-500 platform. The assembly of transcripts from all four types of tissues generated 128,856 unigenes, of which 99,020 were mapped to several public databases for functional annotation. Differentially expressed genes (DEGs) were identified via the comparison of gene expression levels between leaves and other tissues (flowers, roots, and stems). Multiple genes encoding pivotal enzymes, such as squalene synthase (SS), or transcription factors (TFs) related to triterpenoid saponin biosynthesis were identified and further analyzed. The expression levels of unigenes encoding important enzymes were verified by quantitative real-time PCR (qRT-PCR). Different chemical constituents of triterpenoid saponins were identified by Ultra-Performance Liquid Chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS). Conclusions: Our results greatly extend the public transcriptome dataset of C. gracile and provide valuable information for the identification of candidate genes involved in the biosynthesis of triterpenoid saponins and other important secondary metabolites.

Cnidium monnieri (L.) Cuss (C. monnieri) is one of the most widely used traditional herbal medicines, exhibiting a wide range of pharmacological functions for treating asynodia, trichomonas vaginitis, and osphyalgia. Its important medicinal value comes from its abundance of coumarins. To identify genes involved in coumarin biosynthesis and accumulation, we analyzed transcriptome data from flower, leaf, root and stem tissues of C. monnieri. A total of 173,938 unigenes with a mean length of 1,272 bp, GC content of 38.79%, and N50 length of 2,121 bp were assembled using the Trinity program. Of these, 119,177 unigenes were annotated in public databases. We identified differentially expressed genes (DEGs) based on expression profile analysis. These DEGs exhibited higher expression levels in flower tissue than in leaf, stem or root tissues. We identified and analyzed numerous genes encoding enzymes involved in coumarin biosynthesis, and verified genes encoding key enzymes using quantitative real-time PCR. Our transcriptome data will make great contributions to research on C. monnieri and provide clues for identifying candidate genes involved in coumarin metabolic pathways.

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Acorus tatarinowii Schott is a well-known Chinese traditional herb. Lignin is the major biologically active ingredient and exerts a broad range of pharmacological effects: it is an antitumor, antioxidant, and bacteriostatic agent, and protects the cardiovascular system.In this study, the transcriptomes of the leaf and rhizome tissues of A. tatarinowii Schott were obtained using the BGISEQ-500 platform. 141,777 unigenes were successfully assembled, of which 76,714 were annotated in public databases. Further analysis of the lignin biosynthesis pathway revealed a total of 107 unigenes encoding eight key enzymes, which were involved in the lignin biosynthetic pathway. Furthermore, the expression of the key genes involved in lignin synthesis in different tissues was identified by quantitative real-time PCR. Analysis of the differentially expressed genes showed that most of the upregulated unigenes were enriched in rhizome tissues. In addition, 2,426 unigenes were annotated to the transcriptome factor (TF) family. Moreover, 16 TFs regulating the same key enzyme (peroxidase) were involved in the lignin synthesis pathway. The alignment of peroxidase amino acid sequences and the analysis of the structural characteristics revealed that the key peroxidase enzyme had well-conserved sequences, spatial structures, and active sites. This study is the first to provide comprehensive genetic information on A. tatarinowii Schott at the transcriptional level, and will facilitate our understanding of the lignin biosynthesis pathway.