Transcriptome and metabolome analyses reveal anthocyanins pathways associated with fruit color changes in plum...

Plum (Prunus salicina Lindl.) is one of the most widely cultivated and important fruit trees in temperate and cold regions. Fruit color is a significant trait relating to fruit quality in plum. However, its development mechanism has not been studied from the aspects of transcriptional regulation and metabolomic progress. To reveal the mechanism of fruit color developments in plums, we selected the fruits of two plum cultivars, 'Changli84' (Ch84, red fruit) and 'Dahuangganhe' (D, yellow fruit) as plant materials for transcriptome sequencing and metabolomic analysis were performed. Based on the data of transcriptome and metabolome at three fruit developmental stages, young fruit stage, color-change stage, and maturation stage, we identified 2,492 differentially expressed genes (DEGs) and 54 differential metabolites (DMs). The KEGG analysis indicated that "Flavonoid biosynthesis" was significantly enriched during three fruit development stages. Some DEGs in the "Flavonoid biosynthesis" pathway, had opposite trends between Ch84 and D, including chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and flavonol synthase (FLS). Also, the genes encoding MYB-bHLH-WD (MBW) protein complexes, especially MYBs and bHLHs, showed a close relationship with plum fruit color. In the current study, DMs like procyanidin B1, cyanidin 3-glucoside, and cyanidin-3-O-alpha-arabinopyranoside were key pigments (or precursors), while the carotene and carotenoids did not show key relationships with fruit color. In conclusion, the anthocyanins dominate the color change of plum fruit. Carotenes and carotenoids might be related to the color of plum fruit, but do not play a dominate role.