Ethylene accelerates grape ripening <i>via</i> increasing <i>VvERF75</i>-induced ethylene synthesis and chlorophyll degradation

Ethylene plays an important role in grape ripening, acting through ethylene response factors (ERFs) that are downstream of ethylene signaling pathways, yet little else is known about these molecular mechanisms. In our study, we demonstrate that ethylene treatment promotes grape ripening and that the transcription factor VvERF75 shows increased expression during grape ripening. VvERF75 was found to contain a conserved AP2/ERF domain, to be a member of the ERF IXa subfamily, and to localize to the nucleus and to have transactivation activity in yeast. Our in vitro assays showed that VvERF75 can positively regulate expression of pheophorbide a oxygenase (VvPAO1) and 1-aminocyclopropane-1-carboxylic acid synthase (VvACS5) by binding to DRE motifs in their promoters. Overexpression of VvERF75 in tomato increased ethylene production and resulted in dwarfed plants, early flowering and fruit ripening, increased SlPAO and SlACS transcript levels, and decreased chlorophyll content. In general, our study revealed that VvERF75 may regulate fruit ripening by promoting ethylene biosynthesis and chlorophyll degradation, a discovery that lays a foundation for deciphering the molecular mechanisms of grape ripening.