Schematic model of the regulation of the apple peel degreening regulatory module. The increased Ser repeat number in the coding region of ERF17 enhances its transcriptional regulatory activity and its binding ability to the promoter of Chl degradation-related genes. NYC and PPH are required for Chl degradation, which can contribute to apple fruit pigment. An elevated expression level of NYC and PPH improves apple fruit peel degradation and promotes pigment accumulation.