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

Abstract

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 <italic>VvERF75</italic> shows increased expression during grape ripening. <italic>VvERF75</italic> was found to contain a conserved AP2/ERF domain, to be a member of the ERF IXa subfamily, an to localize to the nucleus and to have transactivation activity in yeast. Our in vitro assays showed that <italic>VvERF75</italic> can positively regulate expression of <italic>pheophorbide</italic> a<italic> oxygenase</italic> (<italic>VvPAO1</italic>) and <italic>1-aminocyclopropane-1-carboxylic acid synthase</italic> (<italic>VvACS5</italic>) by binding to DRE motifs in their promoters. Overexpression of <italic>VvERF75</italic> in tomato increased ethylene production and resulted in dwarfed plants, early flowering and fruit ripening, increased <italic>SlPAO</italic> and <italic>SlACS</italic> transcript levels, and decreased chlorophyll content. In general, our study revealed that <italic>VvERF75</italic> 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.