A model of the regulatory acetylation module, MdERF4–MdTPL4–MdHDA19, involved in apple fruit ripening. A C–G mutation in MdERF4 EAR motif reduces the deacetylation activity of the module, which will facilitate the histone acetylation and more accessible chromatin on the promoters of ripening genes, such as MdACS3a in early-maturing apple cultivars.