Metabolomic and Transcriptomic Analysis of the Anthocyanin Regulatory Networks in Malus Domestica Borkh. Peel with Different Color Patterns

Background:Coloring is an important external quality of ‘Fuji’ apple (Malus domestica Borkh.) and there are two color patterns of apple peels, i.e., stripe and blush. The objectives of this study were to reveal the anthocyanin biosynthesis metabolic pathway in striped and blushed peels of Malus domestica using metabolomics and transcriptomics, to identify different anthocyanin metabolites, and to analyze the differentially expressed genes involved in anthocyanin biosynthesis.Result:The metabolite concentration and gene expression were profiled in the striped and blushed fruit peels of apple harvested at three ripening periods to elucidate the color formation mechanism. At the green fruit period, there were 83 DAMs,including 30 flavonoids, 674 DEGs (521 up-regulated and 153 down-regulated),including 3 MYB related genes (up-regulated, LOC103415449, LOC103421948, LOC103432338) and 2 bHLH genes(up-regulated, LOC103436250, LOC103437863) between striped and blushed apple.At the color turning period, there were 48 DAMs,including 20 flavonoids, 880 DEGs (274 up-regulated and 606 down-regulated), including 3 differentially expressed E2.3.1.133, HCT genes(down-regulated), 2 differentially expressed F3H genes (down-regulated), 1 differentially expressed BZ1 gene (down-regulated) and 2 differentially expressed ANS genes (up-regulated) and 2 up-regulated MYB related genes (LOC103411576, LOC103412495), 5 down-regulated MYB related genes(LOC103400953, LOC103408672, LOC103415404, LOC103420697, LOC103421948), 1 differentially expressed bHLH gene(down-regulated, LOC103400870). At the complete coloring period，there were 95 DAMs,including 34 flavonoids, 2258 DEGs (1159 up- and 1099 down-regulated), including 3 differentially expressed E2.3.1.133, HCT genes(down-regulated), 1 differentially expressed E2.3.1.133, HCT genes(up-regulated), 2 differentially expressed CYP98A genes (up-regulated), 4 differentially expressed CHS genes (up-regulated), 2 differentially expressed E5.5.1.6 genes(up-regulated), 2 differentially expressed CYP75B1 genes (up-regulated), 2 differentially expressed F3R genes (up-regulated), 2 differentially expressed ANS genes (up-regulated), 1 differentially expressed DFR genes (up-regulated), 2 differentially expressed BZ1 genes (up-regulated) and 1 differentially expressed MYB related gene (up-regulated, LOC103401575) .There were both 10 kinds of cyanidin in apple peel at color turning period and complete coloring period, Keracyanin and Cyanin were up-regulated at color turning period and Cyanidin-3-O-(6''-O-malonyl)glucoside was up-regulated at complete coloring period.Conclusions: Our researches provide important information on the anthocyanin metabolites and the candidate genes involved in the anthocyanin biosynthesis pathways of Fuji apple in M.domestcia.