Grape white rot is a fungal disease caused by Coniella diplodiella (Speg.) Sacc. that seriously affects fruit quality and yield; however, the underlying mechanism governing the plant response to C. diplodiella pathogens is still poorly understood. Here, we characterized a homeodomain (HD) transcription factor from grape (Vitis vinifera), VvOCP3, and demonstrated its significance in C. diplodiella resistance. Expression analysis showed that VvOCP3 expression was significantly down-regulated upon inoculation with C. diplodiella. Functional analysis with transient injection in grape berries and stable overexpression in grape calli demonstrated that VvOCP3 negatively regulates grape resistance to C. diplodiella. Further studies showed that VvOCP3 directly binds to the promoter of VvPR1 (pathogenesis-related protein 1) and inhibits its expression, resulting in reduced resistance to C. diplodiella. In addition, VvOCP3 can interact with the type 2C protein phosphatase VvABI1, which is a negative modulator of the ABA signaling pathway. In summary, our findings suggest that VvOCP3 plays a crucial role in regulating white rot resistance in grape, and offer theoretical guidance for developing grape cultivars with enhanced C. diplodiella resistance by regulating the expression of VvOCP3.

Anthocyanins are important pigments and nutrients in fruits. Red grape is popular because of the high anthocyanin content. Previous studies have identified VvMYBA1 and its homologs as key regulators of fruit color; however, other transcription factors (TFs) that contribute to fruit color remain poorly understood. The present study identified the R2R3-MYB TF VvMYB24, whose gene expression levels were significantly higher in red berries (L51, Vitis vinifera × Vitis labrusca L.) than in green berries (L20, V. vinifera × V. labrusca L.). Overexpression of VvMYB24 in grape calli increased anthocyanin biosynthesis by upregulating the expression of specific structural genes (VvDFR and VvUFGT). Furthermore, VvMYB24 interacted with VvMYBA1 to form a protein complex that additionally increased the expression of VvDFR and VvUFGT. In addition, light-responsive TF VvHY5 could bind to the VvMYB24 promoters to activate its transcription. Taken together, the results reveal a regulatory module, VvHY5-VvMYB24-VvMYBA1, that influences anthocyanin biosynthesis in grape.