A Comprehensive Multiomics Approach Illuminates the Biosynthetic Mechanism of Scoparone in <i>Artemisia capillaris</i>

Artemisia capillaris, a traditional Chinese medicinal plant, has displayed favourable effects in the treatment of jaundice, inflammation of the liver and cholecystitis for thousands of years. However, the biosynthesis of scoparone, the major active component in A. capillaris, remains unclear. Here, a full-length transcriptomic and integrated metabolomic dataset of A. capillaris was generated for the first time. A nearly complete map of the biosynthesis pathway of scoparone was subsequently proposed. Notably, a novel O-methyltransferase, AcOMT1, which catalyses the methylation of scopoletin and isoscopoletin as the final step in the biosynthesis of scoparone, was annotated and characterised using a weighted gene correlation network, phylogenetic analysis, subcellular localisation analysis and enzyme assays. Molecular docking and dynamics simulations demonstrated that AcOMT1 has a stronger and more stable affinity for scopoletin than for isoscopoletin, explaining its greater efficiency and preference for the methylation of scopoletin. Ultimately, by coexpressing AcOMT1, along with the crucial genes responsible for scopoletin biosynthesis in Nicotiana benthamiana, we developed a system for scoparone biosynthesis, yielding 3.03 μg.g^-1 dry weight. This study provides not only a comprehensive understanding of the biosynthetic pathway of scoparone but also new avenues for scoparone production in A. capillaris via synthetic biology and metabolic engineering.