Multi-omics analysis reveals molecular mechanism of flavonol biosynthesis during the formation of petal color in Camellia nitidissima

Background Camellia nitidissima is a rare and prized species of camellia with golden-yellow flowers, and has high ornamental, medicinal and economic value. Previous studies showed that the content of flavonol accumulated greatly in petals during the formation of golden petal. However, the molecular mechanism of golden flower formation in C. nitidissima remains largely unknown. Results In this study, we performed an integrative analysis of transcriptome, proteome, and metabolome of petals at five developmental stages to construct the regulatory network during golden flower formation in C. nitidissima. Metabolome analysis showed that 323 flavonoids were detected, and epically two flavonols, the quercetin and kaempferol glycosides, were highly accumulated in the golden petals. And transcriptome and proteome sequencing suggested that the expression of flavonol biosynthesis genes or proteins was increased in golden petal stage, whereas expression of anthocyanin and proanthocyanidin genes or proteins were decreased. Further investigation revealed that several putative transcription factors, MYBs and bHLHs, were identified as potentially involved in flavonoid biosynthesis. Expression analysis showed that Flavonol Synthase gene 2 (CnFLS2) was specifically overexpressed in petals, and the expression of CnFLS2 of petals at five developmental stages was positively correlated with flavonol content. Overexpression of CnFLS2 in petals increased flavonol content. Furthermore, analysis showed that the jasmonate (JA) pathways was positively correlated with flavonol biosynthesis, and methyl jasmonate (MeJA) treatment induced the expression of CnFLS2 and the accumulation of flavonol. Conclusions This work describes that JA-CnFLS2 module regulates flavonol biosynthesis during golden petal formation in C. nitidissima.