The apple phosphate starvation response transcription factor MdPHR1 positively regulates zinc and cadmium tolerance

MdPHR1 activates the antioxidant system, reduces the accumulation of reactive oxygen species, regulates the expression of genes related to heavy metal detoxification, and reduces plant sensitivity to zinc or cadmium. In the process of the rapid development of industrial and agricultural production, the excessive accumulation of cadmium (Cd) and zinc (Zn) in the soil seriously threatens the survival and development of plants and even endangers human health. Therefore, it is of great significance to explore new genes and mechanisms to regulate heavy metal tolerance in plants. We demonstrated that MdPHR1 (MYB-CC transcription factor) gene expression was markedly up-regulated after Zn or Cd treatment. Moreover, apple callus and transgenic Arabidopsis lines overexpressing MdPHR1 exhibited enhanced tolerance to Zn or Cd stress. The transgenic materials exhibited enhanced activity of essential antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), accompanied by a significant decrease in reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Additionally, enhanced biomass production and elevated chlorophyll levels were observed in the overexpression lines. Moreover, ectopic overexpression of MdPHR1 in Arabidopsis regulated the preserving structural expression of antioxidant synthesis-related genes and heavy metal detoxification-related genes, thereby increasing the activity of antioxidant enzymes and promoting the efflux of Zn or Cd ions. Thus, Zn- or Cd-induced phytotoxicity was significantly mitigated. Collectively, our results demonstrate that MdPHR1 functions as a key positive regulator in plant adaptation to Zn or Cd stress. These findings provide valuable insights for molecular breeding strategies designed to improve crop tolerance to heavy metal stress.