Integrative analysis of small RNA and degradome sequencing reveals the role of miRNAs in monoterpene biosynthesis in linalool-type Cinnamomum camphora.

BACKGROUND: Cinnamomum camphora is a valuable aromatic oil-producing species with significant economic and industrial importance. Linalool, a monoterpenoid compound and a major component of camphor leaf essential oil, is widely used in cosmetics, food, and pharmaceuticals. While microRNAs (miRNAs) are known to regulate terpenoid biosynthesis, their regulatory role in linalool biosynthesis remains largely unexplored. RESULTS: In this study, we performed small RNA and degradome sequencing on three C. camphora samples (H_MAR, H_MAY, and L_MAY) exhibiting significant differences in linalool content. A total of 199 known and 200 novel miRNAs were identified. Among them, 170 differentially expressed miRNAs (DEMs; 83 downregulated and 87 upregulated) were detected between H_MAY and H_MAR, whereas 77 DEMs (45 downregulated and 32 upregulated) were found between H_MAY and L_MAY. Degradome analysis predicted 223 target genes for 52 known miRNAs and 86 targets for 39 novel miRNAs. Network analysis revealed that the miRNA-SPL module may play a critical role in indirectly regulating linalool biosynthesis. Conversely, the miR167-Cca.gene21941 (GPPS) module may directly regulate monoterpene biosynthesis in linalool-type C. camphora. Additionally, miR5368 was found to target Cca.gene21642 (DHDDS) and Cca.gene34720 (GGDR), both of which may contribute directly to linalool biosynthesis. CONCLUSION: These findings enhance the understanding of post-transcriptional regulation in linalool biosynthesis and provide insights for developing genetic improvement strategies for C. camphora.