A NAC transcription factor MdNAC1 enhances cadmium tolerance in apple

Phenotypic, physiological and molecular analyses demonstrate that MdNAC1 enhances plant tolerance to cadmium stress. Cadmium (Cd) is a highly toxic heavy metal that severely impairs the growth and development of crops. NAC transcription factors are key regulators of plant abiotic stress responses, but their roles in apple (Malus domestica) Cd stress responses remain largely unclear. Here, we identified the apple NAC gene MdNAC1, which exhibits elevated transcriptional levels under Cd stress. The increased abundance of MdNAC1 upregulates the expression of antioxidant enzyme genes, thereby significantly enhancing antioxidant enzyme activity in transgenic plants. This in turn lowers reactive oxygen species (ROS) accumulation and alleviates oxidative damage to plant growth and development under cadmium stress. Ectopic expression of MdNAC1 in Arabidopsis reduced Cd accumulation by negatively regulating the expression of Cd uptake and transport genes, thereby enhancing Cd tolerance. Further Quantitative Real-time PCR analysis revealed that the expression of multiple Cd uptake and transport-related genes was suppressed in transgenic apple seedlings to regulate Cd stress resistance. Moreover, MdNAC1 overexpression enhanced biomass and chlorophyll content in transgenic plants under Cd stress. Our findings indicate that MdNAC1 enhances plant tolerance to Cd through multiple mechanisms in both apple and Arabidopsis, including increased antioxidant activity, ROS scavenging, increased biomass production, and regulation of Cd uptake and transport. These findings provide key candidate genes for fruit tree breeding programs and offer novel insights into the regulatory mechanisms mediating Cd stress resistance.