MdVQ12 confers resistance to Valsa mali by regulating MdHDA19 expression in apple

Valine-glutamine (VQ) motif-containing proteins play a crucial role in plant biotic stress responses. Apple Valsa canker, caused by the ascomycete Valsa mali, stands as one of the most severe diseases affecting apple trees. Nonetheless, the underlying resistance mechanism of VQ proteins against this disease has remained largely unexplored. This study reports MdVQ12, a VQ motif-containing protein, as a positive regulator of apple Valsa canker resistance. Genetic transformation experiments demonstrated that MdVQ12 overexpression increased resistance to V. mali, while gene silencing lines exhibited significantly reduced resistance. MdVQ12 interacted with the transcription factor MdWRKY23, which bound to the promoter of the histone deacetylase gene MdHDA19, activating its expression. MdHDA19 enhanced apple resistance to V. mali by participating in the jasmonic acid (JA) and ethylene (ET) signalling pathways. Additionally, MdVQ12 promoted the transcriptional activity of MdWRKY23 towards MdHDA19. Our findings reveal that MdVQ12 enhances apple resistance to V. mali by regulating MdHDA19 expression and thereby regulating the JA and ET signalling pathways, offering potential candidate gene resources for breeding apple Valsa canker-resistant germplasm.