Delineating Molecular Regulatory of Flavonoids Indicated by Transcriptomic and Metabolomics Analysis during Flower...

Flavonoids are pharmacologically active compounds in flowers of Chrysanthemum morifolium 'Boju' (C. morifolium); however, the molecular regulatory network governing flower development remains largely elusive. Flower samples were collected at four stages, namely budding (BD), bud breaking (BB), early blooming (EB), and full blooming (FB), for omics analysis. We revealed distinct transcriptional regulation patterns at these four stages of the flower from the perspective of differentially expressed unigenes (DEGs). There are 152 DEGs shared among the three comparative groups (BD vs. BB, BB vs EB, EB vs FB), wherein the expression of 44 DEGs (including AtADT6, MDL3, and ROMT) continues to be upregulated, and 85 DEGs (including CYP81E, TPS-Cin-1, and TPS-Cin-2) showed persistent downregulation with flower development. Flavonoid-targeted metabolomics identified 118 differentially abundant metabolites (DAMs) in the FB group compared to the BD stage; the top three upregulated and downregulated metabolites are Cyanidin-3-O-(6″-O-malonyl)glucoside-5-O-glucoside, Luteolin-7-O-(6″-caffeoyl)rhamnoside, Kaempferol-3-O-(6″-p-coumaroyl)glucoside and Chrysoeriol-6,8-di-C-glucoside-7-O-glucoside, Kaempferol, Kaempferol-3,7-O-dirhamnoside, respectively. These DAMs were predominantly enriched in "flavonoid biosynthesis", "isoflavonoid biosynthesis", and "flavone and flavonol biosynthesis" pathways. AtADT6, MDL3, ROMT, CYP81E, TPS-Cin-1, and TPS-Cin-2 were correlated with kaempferol. Our findings provide a new idea for interfering with flavonoid production, especially kaempferol, in flowers.