Integrated Transcriptome and Metabolome Analysis Reveals Differential Berberine Biosynthesis in Leaves and Stems of Phellodendron amurense Rupr. Plantlets

Phellodendron amurense Rupr. is a native tree species in China, well known for its significant medicinal value. Its pharmacological activity mainly derives from the abundant isoquinoline alkaloids in its bark. Berberine serves as the key compound underlying the multiple pharmacological effects of P. amurense and exhibits organ-specific accumulation. However, the genetic mechanisms governing this organ-specific accumulation remain unclear. Genes encoding O-methyltransferase (OMT) and cytochrome P450 (CYP) may play an important role in this regulatory process. In this study, by integrating transcriptomic and metabolomic data from the leaves and stems of P. amurense plantlets, we identified core candidate genes and transcription factors (TFs) that regulate the differential biosynthesis of berberine between these two organs. The results showed that 37 metabolites were significantly upregulated in stems, including main medicinal components such as berberine and jatrorrhizine, while 8497 genes were differentially expressed between leaves and stems. Among these, downstream genes in the berberine biosynthesis pathway, including OMTs and CYPs, were predominantly highly expressed in stems. A co-expression regulatory network identified some TFs such as PaBES1, PaWRKY12/13, PaNAC5, and PaMYB12 as the key nodes regulating the differential biosynthesis of berberine. Phylogenetic analysis classified the 97 PaOMTs into four subgroups. Core candidate genes such as PaOMT7 and PaOMT9 were contained in subgroup IV, potentially contributing to the specific modification of characteristic alkaloids in P. amurense. This study reveals the transcriptional regulatory networks underlying the organ-specific accumulation of berberine in P. amurense plantlets, providing key targets and theoretical support for the targeted improvement and development of elite medicinal varieties.