Polyphenol oxidase plays a critical role in melanin formation in the fruit skin of persimmon (Diospyros kaki cv. ‘Heishi’)

•The black pigment in ‘Heishi’ persimmon fruit skin was a kind of melanin.•This melanin deposits on the cell walls of the upper epidermis and subepidermal cells.•Transient overexpression of DkPPO promoted melanin synthesis in persimmon.