Title: Transcriptome and metabolome analyses reveal pathways associated with fruit color in plum (Prunus salicina Lindl.)

Background In order to reveal the mechanism of fruit color changes in plum, two common plum cultivars Changli84 (Ch84, red fruit) and Dahuangganhe (D, yellow fruit) in Northeast China were selected as plant materials. Transcriptome sequencing and metabonomic analyzing were performed at three different developmental stages: young fruit stage, colour-change stage, and maturation stage. Results “Flavonoid biosynthesis” was significantly enriched in the KEGG analysis. Some DEGs in “Flavonoid biosynthesis” pathway had an opposite trend between the two cultivars, such as CHS , DFR and FLS . Also, transcriptional control of MBW (MYB–bHLH–WD) protein complexes showed a close relationship with plum fruit color, especially the expression of MYBs and bHLHs . In the current study, procyanidin B1 and B2 had the highest level at young fruit stage in Ch84 and the content of procyanidin B2 decreased sharply at the color change stage. Conversely, the content of cyanidin increased with the growth of fruit and reached the peak at the maturation stage. Conclusion The content of procyanidin B1 and B2 in plums at young fruit stage might be the leading factors of the matured fruit color. At the maturation stage, the cyanidin produced by procyanidins keeps the color of the fruit red. Correspondingly, genes in “flavonoid biosynthesis” pathway play critical roles in regulating the accumulation of anthocyanin in plum.