Programmed cell death induced by cadmium stress and/or boron deprivation in tobacco (Nicotiana tabacum L.) cultivar Bright Yellow 2 cells

Cadmium (Cd) is one of the most toxic and widespread heavy metal pollutants in soil. As an essential mineral nutrient, boron (B) plays critical roles in physiological processes of plants. In the present study, programmed cell death (PCD) induced by Cd stress and/or B deprivation was assessed and the underlying mechanisms were clarified in suspension-cultured Nicotiana tabacum L. cultivar Bright Yellow 2 (TBY-2) cells. The PCD in TBY-2 cells was analyzed by Hoechst 33258 staining and the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and then, expression analysis of PCD-related genes was performed using quantitative real-time polymerase chain reaction (qPCR) assays. The production of reactive oxygen species (ROS) was determined using fluorescence microscopy of 2,7-dichlorofluorescein diacetate-labeled cells. The levels of lipid peroxides were quantified by the thiobarbituric acid-reactive substances (TBARS) method. Cadmium stress and/or B deprivation treatments induced PCD that was characterized by a significant increase in the percentage of cells stained with Hoechst 33258 or TUNEL-positive cells, and upregulation or downregulation of the expression of PCD-related genes. Treatments with Cd stress and/or B deprivation increased ROS production and the level of lipid peroxides compared to those of the control group. These data showed that in TBY-2 cells Cd stress and/or B deprivation activated ROS signaling pathways, leading to gene expression that was connected with the PCD process.