Physiological and Molecular Regulation of Amaryllidaceae Alkaloid Biosynthesis in Lycoris Species

The genus Lycoris, renowned for its ornamental value and traditional medicinal applications, is a particularly rich source of these bioactive compounds, including galanthamine, lycorine, and haemanthamine, which exhibit a wide spectrum of therapeutic activities such as acetylcholinesterase inhibition, anticancer, antiviral, and anti-inflammatory effects. The increasing demand for these alkaloids, especially galanthamine for Alzheimer’s disease treatment, necessitates a deeper understanding of their biosynthesis and regulatory mechanisms to facilitate sustainable production through biotechnological approaches. This review provides a comprehensive overview of the physiological and molecular regulation of Amaryllidaceae alkaloids (AA) biosynthesis in Lycoris species. We delve into the diversity, distribution, and biological importance of AAs in Lycoris, followed by a detailed examination of the established and proposed biosynthetic pathways, from primary precursors like phenylalanine and tyrosine, through key intermediates such as norbelladine and 4'-O-methylnorbelladine, to the various alkaloid skeletons. The influence of physiological factors, including environmental cues (light, temperature, water availability, nutrient supply), developmental stages, tissue/organ specificity, plant hormones (jasmonates, abscisic acid), and elicitors, on AA accumulation is critically analyzed. Furthermore, we explore the molecular regulatory networks, encompassing the identification and functional characterization of biosynthetic genes (e.g., PAL, C4H, TYDC, NBS, N4OMT, CYP96T1), the role of transcription factors (MYC2, bHLH, WRKY), promoter analysis, and post-transcriptional control mechanisms, notably by microRNAs like miR396. Insights from omics technologies (transcriptomics, metabolomics, proteomics) that have significantly advanced our understanding are also integrated. Finally, existing knowledge gaps are identified, and future research directions are proposed to fully elucidate and harness the biosynthetic potential of Lycoris species for AA production.