背景回顾：Camptothecin and its derivatives are widely used for treating malignant tumors. 

提出问题：Previous studies revealed only a limited number of candidate genes for camptothecin biosynthesis in Camptotheca acuminata, and it is still poorly understood how its biosynthesis of camptothecin has evolved. 

主要研究：Here, we report a high-quality, chromosome-level C. acuminata genome assembly. 

结果1-全基因组复制：We find that C. acuminata experiences an independent whole-genome duplication and numerous genes derive from it are related to camptothecin biosynthesis. 

结果2-喜树碱的合成：Comparing with Catharanthus roseus, the loganic acid O-methyltransferase (LAMT) in C. acuminata fails to convert loganic acid into loganin. Instead, two secologanic acid synthases (SLASs) convert loganic acid to secologanic acid. The functional divergence of the LAMT gene and positive evolution of two SLAS genes, therefore, both contribute greatly to the camptothecin biosynthesis in C. acuminata. 

结论：Our results emphasize the importance of high-quality genome assembly in identifying genetic changes in the evolutionary origin of a secondary metabolite.

 摘 要 

喜树碱（Camptothecin）及其衍生物广泛用于恶性肿瘤的治疗。先前有关喜树（Camptotheca acuminata）的研究仅报道了少数几个参与喜树碱生物合成的基因，关于喜树碱生物合成的演化目前还所知甚少。本文中，作者报道了一个高质量、染色体水平的喜树基因组组装。作者发现喜树经历了一次独立的全基因组复制事件，并且很多来自该次WGD的基因与喜树碱的生物合成相关。与长春花（Catharanthus roseus）相比，喜树中马钱苷酸O-甲基转移酶LAMT并不能将马钱苷酸转变为马钱苷。相反，两个断马钱苷酸合酶SLASs会将马钱苷酸转变为断马钱苷酸。LAMT基因的功能分化和两个SLAS基因的额正向演化，共同作用于了喜树中喜树碱的生物合成。本文的研究揭示了一个高质量的基因组，为次生代谢物演化起源背后遗传变化的鉴定提供了基础。