The formation of grape quality and the mechanism of resistance against foreign pathogens affect the storage stability of fruits during post-harvest handling. Ethylene plays a crucial role in regulating the ripeness of fruits and can be used as an exogenous regulator to resist exogenous pathogens. In this study, we used different concentrations of ethephon for treatment of grape fruits before veraison, analyzed the anthocyanin content, soluble solids, titratable acid, and determined fruit firmness and cell wall metabolism-related enzymes during fruit development. Results showed that exogenous ethephon promoted the early coloration of grape fruits and increased the coloring-related genes myeloblastosis A1(MYBA1), myeloblastosis A2(MYBA2), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3’-hydroxylase gene (F3’H), flavonoid 3’, 5’hydroxylase (F3’5’H), 3-O-flavonoid glucosyltransferase (UFGT), and glutathione S-transferase (GST), softening related genes Polygalacturonase(PG), pectinate lyases(PL) and Pectin methylesterase( PME, as well as ethylene metabolism pathway-related genes 1-aminocyclopropane-1-carboxylic acid synthase 1(ACS1), 1-aminocyclopropane-1-carboxylic acid oxidase 2 (ACO2), ethylene receptor gene(ETR2), and ethylene-insensitive 3 (EIN3). Ethephon treatment also increased soluble solids and decreased titratable acid in grape fruit. Fruits pretreated with ethephon were inoculated with Botrytis cinerea, which led to resistance in grape fruit through activation of the antioxidant system. The expression levels of disease resistance-related genes including VvPAD4, VvPIP1, VvNAC26, VvDREB, VvAPX, Vvpgip, VvWRKY70, VvMYC2, VvNPR1 also increased in inoculated fruit with pathogen following ethephon pretreatment. Furthermore, we monitored ethylene response factor 1(ERF1) transcription factor, which could interact with protein EIN3 during ethylene signal transduction and mediate fruit resistance against B. cinerea infection. Meanwhile, overexpression of VvERF1 vectorin strawberry fruits reduced the susceptibility to B. cinerea infection. We suggest that ethylene can induce resistance in ripened fruits after B. cinerea infection and provide adequate postharvest care.

Phytochrome-interacting factors (PIFs), as the basic helix–loop–helix (bHLH) transcription factors, are the primary signaling partners for phytochromes (PHY) that play a key role in PHY-mediated light signal transduction. At present, there are few studies on PIFs in fruit trees. In order to clarify the status of PIFs in grapevines, we identified members of the grape PIFs family and conducted phylogenetic and expression analysis. We identified PIF1, PIF3, PIF4, and PIF7 in PIFs families of the grapevine (Vitis vinifera L.), which were distributed on four different chromosomes with similar gene structures. Except for the closer relationship with PIF1 of citrus, PIFs of grape were distant from the other fruit species such as apple, pear, peach, and strawberry. The VvPIFs (except VvPIF4) were located in the syntenic block with those from Arabidopsis thaliana, Solanum lycopersicum, or Citrus sinensis. In addition to PIF1, all PIFs in grapevines have conserved active PHYB binding (APB) sequences. VvPIF1 has a conserved PIF1-specific active PHYA binding (APA) sequence, while amino acid mutations occurred in the specific APA sequence in VvPIF3. Interestingly, two specific motifs were found in the PIF4 amino acid sequence. The photoreceptor-related elements in the VvPIFs promoter region were the most abundant. PIF1, LONG HYPOCOTYL 5 (HY5) and PIF3, PIF4, GIBBERELLIC ACID INSENSITIVE 1 (GAI1) may interact with each other and participate together in light signal transduction. The relative expression levels of the VvPIFs showed diverse patterns in the various organs at different developmental stages, of which PIF4 was most highly expressed. Prior to maturation, the expression of PIF4 and PIF7 in the skin of the different cultivars increased, while the expression of all PIFs in the flesh decreased. The transcription level of PIFs in grape leaves was sensitive to changes in lighting and shading. Shading treatment was beneficial for enhancing the transcription level of VvPIFs, but the effect on VvPIF3 and VvPIF4 was time-controlled. We concluded that PIFs in grapevines are both conservative and species-specific. The identification and analysis of grape PIFs could provide a theoretical foundation for the further construction of grape light regulation networks.