The flowers of pagoda tree ( Sophora japonica L.) are white, which limited its ornamental value and caused few researches on its flower color and anthocyanin accumulation. A pink flower mutant (PM) was discovered, which provided an opportunity to investigate anthocyanin biosynthesis in pagoda tree flowers. In this study, the anthocyanin and flavone/flavonol contents in petals of PM and wild type (WT; white flower) were measured. The content of total anthocyanins was significantly higher in the PM than in the WT at four floral stages (S1–S4). There were no significant differences of total flavonol content between these two varieties at each floral stage, indicating that the flavone/flavonol content did not influence flower color, while anthocyanin was a key factor to determine pink flower coloration. Then, transcriptome analysis was performed by using the petals of PM and WT at S1–S4. Differentially expressed genes encoding chalcone synthase, flavanone 3-hydroxylase, flavonol synthase, flavanone 3′-hydroxylase, dihydroflavonol-4-reductase, anthocyanidin synthase, and UDP-glucose: flavonoid-3- O -glucosyltransferase were identified. Importantly, we found that SjDFR2 might be the key gene in anthocyanin accumulation in petals. Transcription factors, SjPAP1, SjMYB111, SjMYB1b, SjMYBL2, SjTT8, and WD40 protein SjTTG1, might play critical roles in regulation of anthocyanin accumulation in petals. Moreover, regulatory factors involved in the phytohormone signal pathway (SjIAA19, SjIAA27, SjAXR3, SjARF20, and SjERS1), and light signal pathway (SjHY5), were also screened out. These results will provide some new insights into the control of flower color in pagoda tree, as well as some candidate genes to breed novel flower colors using molecular methods.

中文翻译：

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转录组分析揭示了参与宝塔树（Sophora japonica L.）花中花青素生物合成的候选基因

宝塔树（ Sophora japonica L.）的花为白色，限制了其观赏价值，对其花色和花青素积累的研究较少。发现了一种粉红色的花突变体（PM），这为研究宝塔树花中的花青素生物合成提供了机会。在这项研究中，测量了 PM 和野生型（WT；白花）花瓣中的花青素和黄酮/黄酮醇含量。在四个花期（S1-S4），PM 中的总花青素含量显着高于 WT。这两个品种在每个花期的总黄酮含量没有显着差异，表明黄酮/黄酮醇含量不影响花色，而花青素是决定粉红色花色的关键因素。然后，通过在 S1-S4 使用 PM 和 WT 的花瓣进行转录组分析。鉴定了编码查耳酮合酶、黄烷酮 3-羟化酶、黄酮醇合酶、黄烷酮 3'-羟化酶、二氢黄酮醇-4-还原酶、花色素合酶和 UDP-葡萄糖的差异表达基因：类黄酮-3-O-葡萄糖基转移酶。重要的是，我们发现 SjDFR2 可能是花瓣中花青素积累的关键基因。转录因子 SjPAP1、SjMYB111、SjMYB1b、SjMYBL2、SjTT8 和 WD40 蛋白 SjTTG1 可能在调节花瓣中的花青素积累中起关键作用。此外，还筛选出涉及植物激素信号通路（SjIAA19、SjIAA27、SjAXR3、SjARF20和SjERS1）和光信号通路（SjHY5）的调控因子。