Genetic Modulation of ROS Scavenging by DgNAC3 Improves Cold Stress Tolerance in Chrysanthemum morifolium

The NAC transcription factor family, which is specific to plants, plays a critical role in responses to low-temperature stress, though its regulatory mechanisms are yet to be fully elucidated. In the present study, the low-temperature-induced gene DgNAC3 was isolated from the chrysanthemum variety 'Jinba'. The open reading frame (ORF) of DgNAC3 spans 1170 base pairs, which translates into a protein composed of 389 amino acids. Cold tolerance is significantly improved in transgenic chrysanthemums through the overexpression of DgNAC3, evidenced by reduced wilting and improved survival rates following low-temperature stress. Under stress conditions, transgenic lines showed decreased malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and superoxide anion (O₂ ^-) concentrations, alongside significantly elevated activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Furthermore, the expression of cold stress-responsive genes, including DgPOD, DgCAT, and DgCu/ZnSOD, increased. These results suggest that DgNAC3 overexpression increases the ability of transgenic lines to scavenge reactive oxygen species (ROS), consequently improving cold stress resistance in chrysanthemums.