MdDREB2A Negatively Modulates Apple Resistance Against <i>Alternaria alternata</i> by Inhibiting <i>MdPR</i> Genes Expression

Leaf spot disease, caused by the fungal pathogen Alternaria alternata f. sp. mali, poses a severe threat to apple production. Pathogenesis-related (PR) genes are crucial for plant immunity, yet their regulatory networks remain poorly understood. Here, we report that MdDREB2A, a transcription factor known for its role in abiotic stress, negatively regulates apple resistance to A. alternata by suppressing the expression of MdPR10 genes. We demonstrated that MdDREB2A overexpression plants exhibited increased susceptibility to A. alternata infection, whereas its knockdown conferred enhanced resistance. Based on DAP-seq analysis, we identified three MdPR10 genes as direct targets of MdDREB2A. This direct repression was confirmed by ChIP-qPCR, EMSA, and dual-luciferase assays, which showed that MdDREB2A binds to the promoters of MdPR10s to inhibit their transcription upon pathogen infection. Furthermore, functional studies revealed that MdPR10 proteins possess antifungal activity, and their overexpression enhanced resistance in apple leaves. Consequently, in MdDREB2A overexpression plants, the suppression of MdPR10s leads to diminished antifungal resistance. This study establishes MdDREB2A as a negative regulator of defense against A. alternata in apple, which operates by repressing the expression of three pathogenesis-related genes, thereby proposing a new strategic direction for developing resistant apple cultivars.