During the course of evolution of land plants, different classes of flavonoids, including flavonols and anthocyanins, sequentially emerged, facilitating adaptation to the harsh terrestrial environment. Flavanone 3β-hydroxylase (F3H), an enzyme functioning in flavonol and anthocyanin biosynthesis and a member of the 2-oxoglutarate-dependent dioxygenase (2-ODD) family, catalyzes the hydroxylation of (2S)-flavanones to dihydroflavonols, but its origin and evolution remain elusive. Here, we demonstrate that functional flavone synthase Is (FNS Is) are widely distributed in the primitive land plants liverworts and evolutionarily connected to seed plant F3Hs. We identified and characterized a set of 2-ODD enzymes from several liverwort species and plants in various evolutionary clades of the plant kingdom. The bifunctional enzyme FNS I/F2H emerged in liverworts, and FNS I/F3H evolved in Physcomitrium (Physcomitrella) patens and Selaginella moellendorffii, suggesting that they represent the functional transition forms between canonical FNS Is and F3Hs. The functional transition from FNS Is to F3Hs provides a molecular basis for the chemical evolution of flavones to flavonols and anthocyanins, which contributes to the acquisition of a broader spectrum of flavonoids in seed plants and facilitates their adaptation to the terrestrial ecosystem.

在陆地植物的进化过程中，不同种类的黄酮类化合物，包括黄酮醇和花青素依次出现，有利于适应恶劣的陆地环境。黄烷酮 3β-羟化酶 (F3H)，一种在黄酮醇和花青素生物合成中起作用的酶，也是 2-酮戊二酸依赖性双加氧酶 (2-ODD) 家族的成员，催化 ( 2S)-黄烷酮到二氢黄酮醇，但它的起源和演变仍然难以捉摸。在这里，我们证明功能性黄酮合酶 Is (FNS Is) 广泛分布在原始陆生植物苔藓中，并且在进化上与种子植物 F3Hs 相关。我们从植物界不同进化枝中的几种苔类植物和植物中鉴定并表征了一组 2-ODD 酶。双功能酶 FNS I/F2H 出现在地草中，FNS I/F3H 在Physcomitrium ( Physcomitrella ) patens和Selaginella moellendorffii 中进化，表明它们代表了规范 FNS Is 和 F3Hs 之间的功能转换形式。从 FNS Is 到 F3Hs 的功能转变为黄酮到黄酮醇和花青素的化学进化提供了分子基础，这有助于在种子植物中获得更广泛的黄酮类化合物，并促进它们对陆地生态系统的适应。