The homeodomain transcription factor VvOCP3 negatively regulates white rot resistance in grape

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.