Identification and Validation of Magnolol Biosynthesis Genes in Magnolia officinalis

Bacterial infections pose a significant risk to human health. Magnolol, derived from Magnolia officinalis, exhibits potent antibacterial properties. Synthetic biology offers a promising approach to manufacture such natural compounds. However, the plant-based biosynthesis of magnolol remains obscure, and the lack of identification of critical genes hampers its synthetic production. In this study, we have proposed a one-step conversion of magnolol from chavicol using laccase. After leveraging 20 transcriptomes from diverse parts of M. officinalis, transcripts were assembled, enriching genome annotation. Upon integrating this dataset with current genomic information, we could identify 30 laccase enzymes. From two potential gene clusters associated with magnolol production, highly expressed genes were subjected to functional analysis. In vitro experiments confirmed MoLAC14 as a pivotal enzyme in magnolol synthesis. Improvements in the thermal stability of MoLAC14 were achieved through selective mutations, where E345P, G377P, H347F, E346C, and E346F notably enhanced stability. By conducting alanine scanning, the essential residues in MoLAC14 were identified, and the L532A mutation further boosted magnolol production to an unprecedented level of 148.83 mg/L. Our findings not only elucidated the key enzymes for chavicol to magnolol conversion, but also laid the groundwork for synthetic biology-driven magnolol production, thereby providing valuable insights into M. officinalis biology and comparative plant science.