AUTHOR=Wang Defu , Wang Jiangran , Wang Yufen , Yao Dongzuo , Niu Yanbing 

TITLE=Metabolomic and Transcriptomic Profiling Uncover the Underlying Mechanism of Color Differentiation in Scutellaria baicalensis Georgi. Flowers

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.884957

DOI=10.3389/fpls.2022.884957

ISSN=1664-462X

ABSTRACT=<p><italic>Scutellaria baicalensis</italic> Georgi. (Chinese skullcap or Huang-qin) is an extremely crucial medicinal plant in the Labiate family, and the color of its flowers naturally appears purple. However, during the long-term cultivation of <italic>S</italic>. <italic>baicalensis</italic>, very few plants of <italic>S</italic>. <italic>baicalensis</italic> also present white and purple-red flower colors under the same ecological conditions. However, the complex metabolic and transcriptional networks underlying color formation in white, purple-red, and purple flowers of <italic>S</italic>. <italic>baicalensis</italic> remain largely unclarified. To gain an insight into this issue, we conducted transcriptome and metabolomic profiling to elucidate the anthocyanin synthesis metabolic pathway in the flowers of <italic>S</italic>. <italic>baicalensis</italic>, and to identify the differentially expressed candidate genes potentially involved in the biosynthesis of anthocyanins. The results showed that 15 anthocyanins were identified, among which cyanidin 3-rutinoside and delphin chloride were the primary anthocyanins, and accumulation was significantly related to the flower color changes of <italic>S</italic>. <italic>baicalensis</italic>. Furthermore, the down-regulation of <italic>SbDFR</italic> (<italic>Sb02g31040</italic>) reduced the anthocyanin levels in the flowers of <italic>S</italic>. <italic>baicalensis</italic>. The differential expression of the <italic>Sb3GT</italic> (<italic>Sb07g04780</italic> and <italic>Sb01g72290</italic>) gene in purple and purple-red flowers affected anthocyanin accumulation, suggesting that anthocyanin levels were closely associated with the expression of <italic>SbDFR</italic> and <italic>Sb3GT</italic>, which play important roles in regulating the anthocyanin biosynthesis process of <italic>S</italic>. <italic>baicalensis</italic> flowers. Transcriptomic analysis revealed that transcription factors WRKY, bHLH, and NAC were also highly correlated with anthocyanin accumulation, especially for NAC35, which positively regulated <italic>SbDFR</italic> (<italic>Sb02g31040</italic>) gene expression and modulated anthocyanin biosynthesis in flower color variation of <italic>S</italic>. <italic>baicalensis</italic>. Overall, this study presents the first experimental evidence for the metabolomic and transcriptomic profiles of <italic>S</italic>. <italic>baicalensis</italic> in response to flower coloration, which provides a foundation for dynamic metabolic engineering and plant breeding, and to understand floral evolution in <italic>S</italic>. <italic>baicalensis</italic> plants.</p>