MdNAC17 Enhances Saline–Alkali Tolerance in Apple by Regulating Reactive Oxygen Species Removal

Saline–alkali stress is a widespread adversity that severely affects plant growth and productivity. Plant-specific NAC transcription factors (TFs) play a crucial role in various pathways associated with stress responses. However, the function of NAC proteins in conferring tolerance to abiotic stress, along with the underlying mechanisms in apple (Malus domestica), remains incompletely understood. In this study, we identified MdNAC17 from the transcriptome of apple leaves under saline–alkali stress. The overexpression of MdNAC17 in apple calli tissue and Malus hupehensis roots significantly improved resistance to saline–alkali stress by enhancing reactive oxygen species (ROS) scavenging. Transgenic apple plants exhibited higher photosynthetic capacity and antioxidant enzyme activity, as well as less membrane damage. In contrast, silencing MdNAC17 using virus-induced gene silencing (VIGS) technology resulted in the opposite phenotype. Furthermore, MdNAC17 is associated with changes in the transcriptional levels of genes involved in Na+/K+ homeostasis. Overall, our results demonstrate that MdNAC17 positively regulates saline–alkali tolerance in apple.