Shanghai Key Laboratory of Plant Functional Genomics and Resources, CAS Center for Excellence in Molecular Plant Sciences Chenshan Science Research Center, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China.
State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
BMC Plant Biol. 2024 Aug 26;24(1):804. doi: 10.1186/s12870-024-05519-1.
2-oxoglutarate-dependent dioxygenase (2ODD) superfamily is the second largest enzyme family in the plant genome and plays diverse roles in secondary metabolic pathways. The medicinal plant Scutellaria baicalensis Georgi contains various flavonoids, which have the potential to treat coronavirus disease 2019 (COVID-19), such as baicalein and myricetin. Flavone synthase I (FNSI) and flavanone 3-hydroxylase (F3H) from the 2ODDs of DOXC subfamily have been reported to participate in flavonoids biosynthesis. It is certainly interesting to study the 2ODD members involved in the biosynthesis of flavonoids in S. baicalensis.
We provided a genome-wide analysis of the 2ODDs of DOXC subfamily in S. baicalensis, a total of 88 2ODD genes were identified, 82 of which were grouped into 25 distinct clades based on phylogenetic analysis of At2ODDs. We then performed a functional analysis of Sb2ODDs involved in the biosynthesis of flavones and dihydroflavonols. Sb2ODD1 and Sb2ODD2 from DOXC38 clade exhibit the activity of FNSI (Flavone synthase I), which exclusively converts pinocembrin to chrysin. Sb2ODD1 has significantly higher transcription levels in the root. While Sb2ODD7 from DOXC28 clade exhibits high expression in flowers, it encodes a F3H (flavanone 3-hydroxylase). This enzyme is responsible for catalyzing the conversion of both naringenin and pinocembrin into dihydrokaempferol and pinobanksin, kinetic analysis showed that Sb2ODD7 exhibited high catalytic efficiency towards naringenin.
Our experiment suggests that Sb2ODD1 may serve as a supplementary factor to SbFNSII-2 and play a role in flavone biosynthesis specifically in the roots of S. baicalensis. Sb2ODD7 is mainly responsible for dihydrokaempferol biosynthesis in flowers, which can be further directed into the metabolic pathways of flavonols and anthocyanins.
2- 酮戊二酸依赖的双加氧酶（2ODD）超家族是植物基因组中第二大的酶家族，在次生代谢途径中发挥着多样化的作用。药用植物黄芩含有各种具有治疗 2019 年冠状病毒病（COVID-19）潜力的黄酮类化合物，如黄芩素和杨梅素。黄酮合成酶 I（FNSI）和黄酮 3-羟化酶（F3H）来自 DOXC 亚家族的 2ODD，已被报道参与黄酮类化合物的生物合成。研究黄芩中参与黄酮类化合物生物合成的 2ODD 成员肯定是很有趣的。
我们对黄芩 DOXC 亚家族的 2ODD 进行了全基因组分析，共鉴定出 88 个 2ODD 基因，其中 82 个根据 At2ODD 的系统发育分析被分为 25 个不同的分支。然后，我们对参与黄酮和二氢黄酮醇生物合成的 Sb2ODD 进行了功能分析。DOXC38 分支的 Sb2ODD1 和 Sb2ODD2 表现出 FNSI（黄酮合成酶 I）的活性，该酶专一地将松属素转化为白杨素。Sb2ODD1 在根中的转录水平显著较高。而来自 DOXC28 分支的 Sb2ODD7 在花中高表达，它编码 F3H（flavanone 3-hydroxylase）。该酶负责催化柚皮素和松属素转化为二氢山奈酚和根皮素，动力学分析表明 Sb2ODD7 对柚皮素有较高的催化效率。
我们的实验表明，Sb2ODD1 可能作为 SbFNSII-2 的补充因子，在黄芩的根中特异性地发挥黄酮类化合物生物合成的作用。Sb2ODD7 主要负责花中二氢山奈酚的生物合成，这可以进一步导向黄酮醇和花青素的代谢途径。
