Combined Transcriptome and Metabolome Analysis Reveals the Flavonoid/Anthocyanin Biosynthesis Pathway in Regulating Blue and White Flowers of Anemone obtusiloba D. Don

Anemone obtusiloba D. Don is a valuable medicinal herb that also possesses considerable ornamental value for its attractive yellow, blue, and white flowers. Previous studies primarily focused on its pharmaceutical properties and the pigmentation of yellow flowers. However, the formation mechanisms underlying blue and white flowers remain unexplored. In this study, we employed transcriptomic and metabolomic approaches to compare the expression profiles of anthocyanin biosynthesis genes and pigment compositions between the blue and white flowers of A. obtusiloba. Key candidate genes were further validated by quantitative real-time PCR (qRT-PCR). Our results showed that six structural genes, such as flavanone 3-hydroxylase (F3H), flavonoid 3′,5′-hydroxylase (F3′5′H), anthocyanin synthases (ANSs), dihydroflavonol 4-reductase (DFR) and anthocyanidin 3-O-glucosyltransferase (3GT), exhibited significantly higher expression levels in blue flowers than in white flowers. Among the differentially accumulated metabolites (DAMs), nine pigments were more abundant in blue flowers. Notably, delphinidin-3-O-sambubioside-5-O-glucoside and cyanidin-3-O-glucoside were detected exclusively in blue flowers. We speculate that blue flower coloration is associated with these up-regulated genes, which may contribute to increased pigment content and diversity. Furthermore, a putative R3MYB-like repressor may be involved in suppressing anthocyanin biosynthesis, as its elevated expression in white flowers was associated with lower transcript levels of structural genes, which may contribute to the white flower phenotype in A. obtusiloba.