Comparative transcriptomic profiling reveals the regulation of terpenoid biosynthesis in Sinocalycanthus chinensis

Sinocalycanthus chinensis, a diploid (2n = 22) deciduous shrub, belongs to the Calycanthaceae family of magnoliids and is rich secondary metabolites, such as terpenoids. However, the regulation of terpenoid biosynthesis in S. chinensis is largely unknown. In this study, comparative transcriptome analyses were performed in the bark, branches, leaves, and flowers. KEGG enrichment analysis revealed that the terpenoid biosynthesis and cytochrome P450 pathways were significantly enriched in the four tissues. Twelve terpenoid backbone biosynthesis-related genes were identified, and eight terpene synthases (TPSs) were reassembled based on independent transcriptomes from the four tissues. Phylogenetic analysis of the TPSs showed high sequence similarity between S. chinensis and Arabidopsis, and these TPSs were classified into three subfamilies. Moreover, 39 phytohormone response-related genes, including 5 abscisic acid (ABA) receptors, 25 auxin response factors, 3 gibberellin (GA) response genes, 5 ethylene response genes, and 1 jasmonic acid (JA) response gene were analyzed. Most phytohormone pathway-related genes were upregulated in the flowers and downregulated in the leaves. The endogenous indole acetic acid (IAA) content was higher in the flowers than in the other comparisons. Our results provide an opportunity to reveal the regulation of terpenoid biosynthesis in S. chinensis.