Transcriptome analysis reveals novel genes involved in anthocyanin biosynthesis in the flesh of peach

Peach is an important deciduous fruit tree species. Anthocyanins play an important role in fruit color formation and, through linkage analysis, previous studies have identified and mapped the key genes regulating anthocyanins' accumulation to chromosomes 3 and 5 in two different germplasms. To understand the overall regulatory network of anthocyanins biosynthesis, genes co-expressed with these key genes were identified in the red-fleshed 'Tianjin Shui Mi' and white-fleshed 'Hakuho' germplasms. Analysis of their flesh anthocyanin contents revealed differences 15 days before maturation. Therefore, transcriptome analysis of the flesh of fruits belonging to these two germplasms was performed to search for genes that were up-regulated at the late stage of development of 'Tianjin Shui Mi' but not of 'Hakuho', and identified 183 genes. These genes were also analyzed in the flesh transcriptomes of peach fruits belonging to 30 peach varieties with different anthocyanin contents at maturation, and the Pearson's correlation coefficients between their expression levels and anthocyanin contents were determined. The results showed that 66 genes were significantly correlated to anthocyanin contents, most of which previously reported as regulatory, biosynthetic, and transporter genes involved in anthocyanins' regulatory network. The results of this study enrich the understanding of key genes involved in the biological pathway regulating anthocyanins biosynthesis. The genes mostly associated with anthocyanins biosynthesis presented in this study are of great importance for molecular marker-assisted breeding.