Department of Science, Graduate School of Science and Technology, Shinshu University, Asahi 3-1-1, Matsumoto, Nagano, 390-8621 Japan.
Department of Biology, Faculty of Science, Shinshu University, Asahi 3-1-1, Matsumoto, Nagano, 390-8621 Japan.
Plant Cell Physiol. 2023 Jun 15;64(6):637-645. doi: 10.1093/pcp/pcad024.
Aurones constitute one of the major classes of flavonoids, with a characteristic furanone structure that acts as the C-ring of flavonoids. Members of various enzyme families are involved in aurone biosynthesis in different higher plants, suggesting that during evolution plants acquired the ability to biosynthesize aurones independently and convergently. Bryophytes also produce aurones, but the biosynthetic pathways and enzymes involved have not been determined. The present study describes the identification and characterization of a polyphenol oxidase (PPO) that acts as an aureusidin synthase (MpAS1) in the model liverwort, Marchantia polymorpha. Crude enzyme assays using an M. polymorpha line overexpressing MpMYB14 with high accumulation of aureusidin showed that aureusidin was biosynthesized from naringenin chalcone and converted to riccionidin A. This activity was inhibited by N-phenylthiourea, an inhibitor specific to enzymes of the PPO family. Of the six PPOs highly induced in the line overexpressing MpMyb14, one, MpAS1, was found to biosynthesize aureusidin from naringenin chalcone when expressed in Saccharomyces cerevisiae. MpAS1 also recognized eriodictyol chalcone, isoliquiritigenin and butein, showing the highest activity for eriodictyol chalcone. Members of the PPO family in M. polymorpha evolved independently from PPOs in higher plants, indicating that aureusidin synthases evolved in parallel in land plants.
橙酮类化合物是类黄酮的主要类别之一，具有作为类黄酮 C 环的特征呋喃酮结构。各种酶家族的成员参与不同高等植物中的橙酮生物合成，这表明在进化过程中，植物独立地和趋同地获得了生物合成橙酮的能力。苔藓植物也产生橙酮，但生物合成途径和涉及的酶尚未确定。本研究描述了在模式苔藓植物 Marchantia polymorpha 中鉴定和表征一种作为 aureusidin 合酶 (MpAS1) 的多酚氧化酶 (PPO)。使用过表达 MpMYB14 的 M. polymorpha 系进行的粗酶测定，该基因高度积累 aureusidin，表明 aureusidin 是从柚皮素查尔酮生物合成的，并转化为 riccionidin A。这种活性被 N-苯硫脲抑制，N-苯硫脲是 PPO 家族酶的特异性抑制剂。在过表达 MpMyb14 的系中高度诱导的六个 PPO 之一，MpAS1，当在酿酒酵母中表达时，发现它可以从柚皮素查尔酮生物合成 aureusidin。MpAS1 还识别橙皮素查尔酮、异甘草素和白杨素，对橙皮素查尔酮表现出最高的活性。M. polymorpha 中的 PPO 家族成员独立于高等植物中的 PPO 进化而来，表明 aureusidin 合酶在陆生植物中平行进化。
