Ethylene response factors regulate ethylene biosynthesis and cell wall modification in persimmon (Diospyros kaki L.) fruit during ripening

Abstract Ethylene plays an essential role in climacteric fruit ripening via the ethylene signaling pathway. Ethylene response factor (ERF) is a critical downstream component of the ethylene signaling pathway. However, the transcriptional regulatory mechanism underlying ERF in persimmon fruit ripening remains poorly understood. Here, we explored the role of DkERF8/16/18 in regulating persimmon fruit ripening. Transmission electron microscopy showed that persimmon fruit softening was associated with middle lamella degradation and cell wall swelling and distortion. The expression of five ERF genes (DkERF8/16/18/19/24), twelve cell-wall-modifying genes (DkPG1, DkPL1, DkPE1/2, Dkβ-GAL1, DkEGase1, DkXTH2/9/10/11, DkMAN1, DkEXP4) and four ethylene biosynthesis genes (DkACS1/2, DkACO1/2) was induced by ethylene and suppressed by 1-MCP during persimmon fruit storage. Dual luciferase assays, site mutations and electrophoretic mobility shift assays indicated that DkERF8 and DkERF16 activate DkXTH11 and DkEXP4, respectively, by binding to their promoters. DkERF18 binds to the DkACS2 promoter, increasing its activity. Transient overexpression of DkERF8 promotes the conversion of acid soluble pectin to water soluble pectin in persimmon fruit. Moreover, transient overexpression of DkERF18 resulted in increased ethylene production. These results suggest that DkERF8/16/18 may be involved in persimmon fruit ripening by promoting cell wall modification and ethylene biosynthesis.