Oroxylum indicum (L.) Kurz is a medicinally important and rare tree species of the family Bignoniaceae. It is rich in flavonoid content and its mature roots are extensively used in Ayurvedic formulations. O. indicum specific flavonoids like oroxylin B, prunetin and oroxindin possess antibacterial, antiproliferative, antioxidant and anticancerous properties, signifying its importance in modern medicine. In the present study, de novo transcriptome analysis of O. indicum root was performed to elucidate the genes involved in flavonoid metabolism. A total of 24,625,398 high quality reads were assembled into 121,286 transcripts with N50 value 1783. The BLASTx search of 81,002 clustered transcripts against Viridiplantae Uniprot database led to annotation of 46,517 transcripts. Furthermore, Gene ontology (GO) revealed that 34,231 transcripts mapped to 3049 GO terms and KEGG analysis demonstrated that 4570 transcripts plausibly involved in 132 biosynthetic pathways. The transcriptome data indicated that cinnamyl-alcohol dehydrogenase (OinCAD) was abundant in phenylpropanoid pathway genes while; naringenin chalcone synthase (OinCHS), flavone synthase (OinFNS) and flavonoid 3', 5'-methyltransferase (OinF35 MT) were abundant in flavonoid, isoflavonoid, flavone and flavonol biosynthesis pathways, respectively. Transcription factor analysis demonstrated the abundance of MYB, bHLH and WD40 transcription factor families, which regulate the flavonoid biosynthesis. Flavonoid pathway genes displayed differential expression in young and old roots of O. indicum. The transcriptome led to the identification of 31 diverse full length Cytochrome P450 (CYP450) genes which may be involved in biosynthesis of specialized metabolites and flavonoids like baicalein and baicalin. Thus, the information obtained in this study will be a valuable tool for identifying genes and developing system biology approaches for in vitro synthesis of specialized O. indicum metabolites.

中文翻译：

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具有药用价值的稀有树种 Oroxylum indicum 的从头根转录组，用于表征黄酮类生物合成途径

Oroxylum indicum (L.) Kurz 是紫杉科的重要药用树种。它富含类黄酮，其成熟的根被广泛用于阿育吠陀配方。O. indicum 特定的黄酮类化合物如 oroxylin B、prunetin 和 oroxindin 具有抗菌、抗增殖、抗氧化和抗癌特性，表明其在现代医学中的重要性。在本研究中，对籼稻根进行了从头转录组分析，以阐明参与类黄酮代谢的基因。总共 24,625,398 个高质量读数被组装成 121,286 个转录本，N50 值为 1783。BLASTx 搜索针对 Viridiplantae Uniprot 数据库的 81,002 个聚集转录本导致对 46,517 个转录本进行注释。此外，基因本体论 (GO) 揭示了 34、231 个转录本映射到 3049 个 GO 术语，KEGG 分析表明 4570 个转录本可能涉及 132 条生物合成途径。转录组数据表明肉桂醇脱氢酶（OinCAD）在苯丙烷途径基因中含量丰富，而；柚皮素查尔酮合酶 (OinCHS)、黄酮合酶 (OinFNS) 和类黄酮 3'、5'-甲基转移酶 (OinF35 MT) 分别在类黄酮、异黄酮、黄酮和黄酮醇生物合成途径中含量丰富。转录因子分析表明 MYB、bHLH 和 WD40 转录因子家族的丰度，它们调节类黄酮的生物合成。类黄酮通路基因在 O. indicum 的幼根和老根中表现出差异表达。转录组鉴定了 31 个不同的全长细胞色素 P450 (CYP450) 基因，这些基因可能参与特殊代谢物和黄酮类化合物（如黄芩素和黄芩素）的生物合成。因此，本研究中获得的信息将成为鉴定基因和开发系统生物学方法的宝贵工具，用于体外合成专门的 O. indicum 代谢物。