Apple <scp>EBF1</scp> / <scp>CML15</scp> – <scp>VQ8</scp> module bridges ethylene and calcium signaling to modulate salt‐induced anthocyanin accumulation

Although previous studies have shown that plants enhance salt tolerance by accumulating anthocyanins, the molecular mechanisms regulating salt stress-induced anthocyanin biosynthesis remain unclear. This study establishes a regulatory network for salt-induced anthocyanin accumulation in apple (Malus × domestica), centered on the VALINE-GLUTAMINE (VQ) protein MdVQ8. MdVQ8 promotes anthocyanin biosynthesis via a dual-safeguard pathway: enhancing MdWRKY75-mediated transcriptional activation of the key regulator MYELOBLASTOSIS 1 (MdMYB1), and facilitating the TEOSINTE BRANCHED1/CYCLOIDEA/PCF 46 (MdTCP46)-MdMYB1 interaction. The calcium (Ca²⁺) signaling regulator CALMODULIN-LIKE PROTEIN 15 (MdCML15) maintains the MdVQ8-MdWRKY75 and MdVQ8-MdTCP46 complexes, thereby amplifying MdVQ8-induced anthocyanin biosynthesis under salt stress. Additionally, the ethylene signaling repressor ETHYLENE INSENSITIVE3-BINDING F-BOX PROTEIN 1 (MdEBF1) counteracts MdVQ8 function by promoting its ubiquitination and degradation. Our findings reveal that the MdEBF1/MdCML15-MdVQ8 module coordinates the MdWRKY75-MdMYB1 and MdTCP46-MdMYB1 pathways to regulate salt-induced anthocyanin accumulation. Therefore, these results offer new insights into the coordinated regulation of salt stress responses and anthocyanin biosynthesis by Ca²⁺ and ethylene signaling.