Flavonoids are a class of secondary metabolites widely distributed in plants. Regiospecific modification by methylation and glycosylation determines flavonoid diversity. A rare flavone glycoside, diosmin (luteolin-4′-methoxyl-7-O-glucosyl-rhamnoside), occurs in Chrysanthemum indicum. How Chrysanthemum plants evolve new biosynthetic capacities remains elusive. Here, we assemble a 3.11-Gb high-quality C. indicum genome with a contig N50 value of 4.39 Mb and annotate 50,606 protein-coding genes. One (CiCOMT10) of the tandemly repeated O-methyltransferase genes undergoes neofunctionalization, preferentially transferring the methyl group to the 4′-hydroxyl group of luteolin with ortho-substituents to form diosmetin. In addition, CiUGT11 (UGT88B3) specifically glucosylates 7-OH group of diosmetin. Next, we construct a one-pot cascade biocatalyst system by combining CiCOMT10, CiUGT11, and our previously identified rhamnosyltransferase, effectively producing diosmin with over 80% conversion from luteolin. This study clarifies the role of transferases in flavonoid diversity and provides important gene elements essential for producing rare flavone.

黄酮类化合物是一类广泛分布于植物中的次生代谢产物。甲基化和糖基化的区域特异性修饰决定了类黄酮的多样性。一种罕见的黄酮苷，地奥司明（木犀草素-4'-甲氧基-7-O-葡萄糖基-鼠李糖苷），存在于野菊花中。菊花植物如何进化出新的生物合成能力仍然是个谜。在这里，我们组装了一个 3.11-Gb 的高质量C. indicum基因组，其重叠群 N50 值为 4.39 Mb，并注释了 50,606 个蛋白质编码基因。串联重复的 O-甲基转移酶基因之一 ( CiCOMT10 ) 经历新功能化，优先将甲基转移到具有邻位取代基的木犀草素的 4'-羟基上，形成香叶木素。此外，CiUGT11 (UGT88B3) 特异性地葡萄糖基化香叶素的 7-OH 基团。接下来，我们通过结合 CiCOMT10、CiUGT11 和我们之前鉴定的鼠李糖基转移酶构建了一锅级联生物催化剂系统，有效地生产地奥司明，木犀草素的转化率超过 80%。这项研究阐明了转移酶在类黄酮多样性中的作用，并提供了生产稀有黄酮所必需的重要基因元件。