MdMYB48, an R2R3 MYB transcription factor, regulates root growth and drought tolerance in apple

Drought is a major abiotic stress that limits the growth and productivity of apple ( Malus domestica ), a perennial fruit crop with a high dependence on water availability. R2R3-MYB transcription factors play key roles in stress responses, however, their specific functions in coordinating root development and drought tolerance in apple remain underexplored. Here, we identified and functionally characterized MdMYB48, an R2R3-MYB gene that is responsive to drought and abscisic acid (ABA) in apple ( Malus domestica ). Phylogenetic and microsynteny analyses revealed that MdMYB48 is evolutionarily conserved across multiple eudicot species, including Arabidopsis , and belongs to the MYB subgroup 2R-11. MdMYB48 encodes a nuclear-localized transcriptional activator whose expression is significantly induced by drought and ABA. Overexpression of MdMYB48 in both apple and Arabidopsis enhanced primary root elongation and lateral root formation under both normal and drought stress conditions. Transgenic lines exhibited improved drought tolerance, characterized by reduced ROS accumulation, elevated proline content, and higher survival rates. Gene expression analysis showed that MdMYB48 activates the transcription of key stress-related genes, including MdRD22 , MdDREB1 , and MdNCED3 . Chromatin immunoprecipitation assays confirmed that MdMYB48 directly binds to the promoters of MdRD22 and MdNCED3 , supporting its role as a transcriptional regulator in the ABA-mediated drought response. These findings provide novel insights into the transcriptional control of drought adaptation in woody fruit crops and highlight MdMYB48 as a promising candidate for enhancing drought resilience.