Targeted Metabolome and Transcriptome Analyses Reveal the Molecular Mechanism of Color Variation between Sepals and Petals in Fuchsia hybrida

The sepal color of Fuchsia hybrida is colorful instead of green and usually varies from the petal colors, which greatly increases its ornamental value and attract customers' preference. However, the potential molecular mechanism underlying the color variation between sepals and petals remains unclear. The present study collected F. hybrida with red sepals and purple petals to explore the key pigments and genes involved in color development using a targeted metabolome and transcriptome. A total of 43 metabolites with diverse hydroxylation, glycosylation, methylation and acylation patterns were isolated and identified by UPLC-MS/MS. The quantification analysis showed that peonidin-3,5-O-diglucoside and malvidin-3,5-O-diglucoside were the most abundant anthocyanins accumulating in the sepals and petals, respectively. Then, six libraries from the sepals and petals were constructed for the transcriptome and 70,135 unigenes were generated. The transcript level of FhF3 ' H was significantly higher in the sepals, while Fh3 ' 5 ' H showed more abundant expression in the petals, which can account for the abundant peonidin and malvidin accumulation in the sepals and petals, respectively. The subsequent multiomics analysis showed that both the differentially accumulated anthocyanins and expressed unigenes were enriched in the anthocyanin biosynthesis pathway. Additionally, FhMYBs potentially regulating anthocyanin biosynthesis were screened out by correlation analysis and protein interaction prediction. These findings help to elucidate the molecular mechanisms underlying the color variation between the sepals and petals in F. hybrida.