Sichuan Zoige Alpine Wetland Ecosystem National Observation and Research Station, Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Science, Sichuan University, Chengdu, 610065, China.
State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystem, College of Ecology, Lanzhou University, Lanzhou, 730000, China.
Plant J. 2024 Nov;120(3):1176-1189. doi: 10.1111/tpj.17046. Epub 2024 Sep 27.
Ilex is known for its rich content of secondary metabolites, particularly triterpenoid saponins. These compounds hold significant value in natural remedies and herbal medicine. However, the molecular mechanisms responsible for triterpenoid biosynthesis in plants of this genus remain largely unexplored. In this study, we successfully generated the first chromosome-scale genome of Ilex hylonoma. The assembly, comprising 20 anchored chromosomes, has an N50 contig size of 2.13 Mb and a scaffold size of 33.68 Mb. Comparative genome analyses with two other congeners with available chromosome-level genomes suggested that an end-to-end chromosome fusion event likely contributed to the reduction in chromosome number from n = 20 to n = 19 within this genus. By integrating transcriptomic and metabolomic data, we identified the gene expression patterns and metabolite profiles of I. hylonoma across three commonly utilized medicinal tissues. We subsequently pinpointed candidate genes involved in the regulation of triterpenoid saponin biosynthesis, including CYP450 genes, UGT genes, and associated transcription factors. Furthermore, yeast heterologous expression analysis revealed that ihyl08363 catalyzed the conversion of β-amyrin into oleanolic acid, while ihyl04303 catalyzed the C-2α hydroxylation of oleanolic acid to produce maslinic acid. This integrated analysis provides valuable insights into the biosynthesis of important triterpenoid saponins in medicinal Ilex plants.
冬青属以其丰富的次生代谢产物而闻名，特别是三萜皂苷。这些化合物在天然药物和草药中具有重要的价值。然而，该属植物中三萜生物合成的分子机制在很大程度上仍未被探索。在这项研究中，我们成功地生成了冬青属的第一个染色体规模的基因组。组装结果包含 20 个锚定染色体，N50 片段大小为 2.13Mb，支架大小为 33.68Mb。与另外两个具有染色体水平基因组的近缘种进行比较基因组分析表明，端到端的染色体融合事件可能导致该属的染色体数目从 n=20 减少到 n=19。通过整合转录组和代谢组数据，我们鉴定了三种常用药用组织中冬青属的基因表达模式和代谢物图谱。随后，我们确定了参与三萜皂苷生物合成调控的候选基因，包括 CYP450 基因、UGT 基因和相关转录因子。此外，酵母异源表达分析表明，ihyl08363 催化 β-香树脂醇转化为齐墩果酸，而 ihyl04303 催化齐墩果酸的 C-2α 羟化生成马桑酸。这项综合分析为药用冬青植物中重要三萜皂苷的生物合成提供了有价值的见解。
