Platycodon grandiflorus, known as balloon flower, has been widely used in East Asian medicine to treat respiratory and inflammatory disorders. Its pharmacological activity is largely attributed to oleanane-type triterpenoid saponins, particularly platycodins, which exhibit anti-inflammatory, hepatoprotective, and anti-tumor effects. However, the complete biosynthetic pathway of these compounds has remained unresolved due to fragmented reference genomes and unclear gene–enzyme relationships. The absence of a high-quality genome has limited the systematic identification of pathway-related genes and regulatory mechanisms. Based on these challenges, there is a need for comprehensive genomic analysis to elucidate the biosynthesis and diversification of these bioactive saponins.
A research team from Anhui University of Chinese Medicine and collaborating institutions has generated the first telomere-to-telomere (T2T) gap-free genome of P. grandiflorus. The findings (10.1093/hr/uhaf030) were published on May 1, 2025, in Horticulture Research. By combining full-length genome assembly with coordinated metabolomic and transcriptomic analyses, the study identifies key enzyme families and candidate genes involved in the biosynthesis of medicinal triterpenoid saponins. This work provides a new foundation for genetic, biochemical, and biotechnological studies of this widely used herbal species.
The researchers assembled a 593.56 Mb genome mapped to nine chromosomes with no unresolved gaps and identified 27,808 protein-coding genes. Comparative analysis revealed an ancient γ-whole genome triplication, while extensive tandem and proximal gene duplications contributed to the expansion of secondary metabolite biosynthesis pathways.
Metabolomic profiling of roots collected in May, August, and October showed that major saponin accumulation peaked in May and October. Corresponding transcriptomic data demonstrated increased expression of key biosynthetic genes during these periods. A total of 13 oxidosqualene cyclases (OSCs) and 211 cytochrome P450s (CYPs) were identified. Phylogenetic and expression analyses highlighted PgOSC7, PgOSC8, and PgOSC9 as likely contributors to β-amyrin scaffold formation. Downstream modifications were associated with three CYP subfamilies: CYP716A, CYP72A, and CYP749A
Correlation analyses identified PgCYP716A3, PgCYP716A15, PgCYP716A18, PgCYP72A3, PgCYP72A8, and PgCYP749A3 as strong candidates responsible for C-2, C-16, C-23, and C-24 hydroxylation steps leading to structural diversification of platycodins. These genes represent priority targets for future functional verification.
“This work provides the first complete genomic blueprint for understanding how P. synthesizes its pharmacologically active triterpenoid saponins,” the authors noted. “By integrating metabolic profiles with gene expression dynamics, we have narrowed down key candidate CYP450s and OSCs responsible for critical modification steps. These findings substantially accelerate biochemical validation and synthetic biology applications aimed at producing rare or high-value saponins.”
The high-quality genome and identified candidate biosynthetic genes enable targeted molecular breeding to enhance saponin yield and composition in P. grandiflorus. The findings also support metabolic engineering strategies to reconstruct platycodin biosynthesis in microbial or plant chassis systems, facilitating sustainable large-scale production. Furthermore, knowledge of CYP-mediated modification steps provides opportunities to design novel saponin derivatives with improved therapeutic properties. Overall, this work establishes a genetic framework that benefits herbal medicine research, pharmaceutical development, and agricultural innovation.
###
References
DOI
10.1093/hr/uhaf030
Original Source URL
https://doi.org/10.1093/hr/uhaf030
Funding information
This work was supported by the National Natural Science Foundation of China (U21A20406), the Excellent Young Scholars Project of Natural Science Foundation of Anhui Province in China (2208085Y30), the Key Project Foundation of Support Program for the Excellent Young Faculties in Universities of Anhui Province in China (gxyqZD2022051), Science Research Project at the Universities of Anhui Province for Distinguished Young Scholars (2023AH020036), Young Elite Scientists Sponsorship Program by CACM (CACM-2023-QNRC2-B23), Traditional Chinese Medicine High-Level Key Discipline Construction Project of National Administration of Traditional Chinese Medicine Science of Chinese Medicinal Material Resources (pharmaceutical botany) (zyyzdxk-2023095), Research Funds of Center for Xin’an Medicine and Modernization of Traditional Chinese Medicine of IHM (2023CXMMTCM008), and China Postdoctoral Science Foundation-Anhui Joint Support Program under grant (2024T030AH).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.