Integrative Analysis of Metabolome and Transcriptome Reveals the Mechanism of Color Formation in Liriope spicata Fruit

Liriope spicata is an important ornamental ground cover plant, with a fruit color that turns from green to black during the development and ripening stages. However, the material basis and regulatory mechanism of the color variation remains unclear. In this study, a total of 31 anthocyanins and 2 flavonols were identified from the skin of L. spicata fruit via integrative analysis on the metabolome and transcriptome of three developmental stages. The pigments of black/mature fruits are composed of five common anthocyanin compounds, of which Peonidin 3-O-rutinoside and Delphinidin 3-O-glucoside are the most differential metabolites for color conversion. Using dual-omics joint analysis, the mechanism of color formation was obtained as follows. The expression of structural genes including 4CL, F3H, F3 ' H, F3 ' 5 ' H and UFGT were activated due to the upregulation of transcription factor genes MYB and bHLH. As a result, a large amount of precursor substances for the synthesis of flavonoids accumulated. After glycosylation, stable pigments were generated which promoted the accumulation of anthocyanins and the formation of black skin.