Integrated transcriptome and targeted metabolomics reveals floral coloration mechanisms in response to light intensity in Argyranthemum frutescens

Light is a crucial environmental factor that influences the plant coloration, yet the mechanisms underlying the color variation responding to light intensity remain unclear. Here, morphology, biochemistry, transcriptome and targeted metabolome analyses were integrated to characterize flower petal color responses and the molecular basis of pigmentation in Argyranthemum frutescens , a worldwide ornamental plant under three light intensities (50, 150 and 600 μmol m –2 s –1 ). It was found that the petals pigmentation and total anthocyanin content significantly increased with the enhanced light intensity. Anthocyanin-targeted metabolome identified a total of 55 metabolites, and 36 differentially accumulated anthocyanins (DAA) were detected. The contents of cyanidins and procyanidins changed significantly in samples under different light intensities. Specifically, cyanidin-3-O-rutinoside and cyanidin-3-O-(6-O-malonyl-beta-D-glucoside) showed a gradual increase with enhanced light intensity, whereas Procyanidin A2 decreased. Transcriptomics showed a gradual increase in the expression of CHI, F3H as well as DFR, which involved in anthocyanin biosynthesis pathways, corresponding to the accumulation of anthocyanin content as light intensified. Moreover, 186 differentially expressed transcription factors (TFs) were identified. The correlation network of gene-to-metabolite between TFs and DEGs encoding biosynthetic enzymes, as well as DAA indicated that the family genes of ERF, bZIP, WRKY, MYB, and NAC play crucial roles in activating light intensity-responsive genes and regulating the flower color in A. frutescens . These findings revealed the potential mechanisms underlying light intensity-induced flower color changes in A. frutescens , which provide a theoretical foundation for its landscape use and flower color improvement of A. frutescens . • Integrated multi-omics analysis characterized light-responsive petal coloration mechanisms in Argyranthemum frutescens . • Light-enhanced pigmentation occurred through progressive accumulation of cyanidin derivatives, particularly cyanidin-3-O-(6-O-malonyl-β-D-glucoside) and cyanidin-3-O-rutinoside. • Upregulation of structural genes in anthocyanin biosynthesis pathways under elevated light intensity. • Light-responsive transcription factors (MYB, NAC, WRKY, bZIP, ERF) activate AfCHS , AfCHI , AfF3H , and AfDFR to enhance anthocyanin accumulation.