Effects of Lead (Pb) and Cadmium (Cd) Elements on Lipid Peroxidation, Catalase Enzyme Activity and Catalase Gene Expression Profile in Tomato Plants

Heavy metals are significant abiotic stress factor, affecting various response mechanisms in plants. These responses include: changes in membrane composition, production of small molecules and free radicals, and alterations in the activities of antioxidant enzymes and their gene expressions. For this reason, lipid peroxidation levels (MDA), catalase enzyme activity, and gene expression profiles, quantified by real-time PCR, were analyzed in tomato plants exposed to various concentrations (0, 80, 160, 320, 640 and 1280 μM) of Cd2+ and Pb2+. All concentration of Cd+2 or Pb+2 contamination led to increased lipid peroxidation and catalase enzyme activity, except for 320 and 640 μM Cd+2 contamination levels. As a result, gene expression patterns at the mRNA level and changes in MDA content under different concentrations of Pb+2 and Cd+2 contamination revealed a positive correlation, although no correlation was found between gene expression patterns at the mRNA level and catalase enzyme activity. These results might be explained by the regulation of genes at the transcriptional, posttranscriptional, and also translational or posttranslational levels.