Cd and Hg Mediated Oxidative Stress, Antioxidative Metabolism and Molecular Changes in Soybean (Glycine max L.)

Cadmium (Cd) and Mercury (Hg) is among the heavy metals most hazardous for plant and human health. Known to induce oxidative stress in plants and disbalance equilibrium in the antioxidant defence system, these metals alter plant growth and cause damage at the cellular and molecular levels. Soybean is an important oilseed crop that is raised in soils often contaminated by Cd and Hg. The comparative studies on the deleterious effect of Cd and Hg and the defence system of antioxidants were not studied earlier in soybean plant. In this study, soy-bean plants were exposed to Cd (100 mu M CdCl2) and Hg (100 mu M HgCl2) and studied for physiological, biochem-ical and molecular responses. Both Cd and Hg treatment increased the magnitude of oxidative stress. Activities of antioxidant enzymes were significantly upregulated in response to Cd and Hg stress. Quantitative and qualitative assessment of isolated RNA showed significant differences in RNA under stress. Integrity values of RNA con-firmed alterations. Transcript level of the Actin gene, involved in the morphogenesis of plants and also used as referenced gene in expression studies was analyzed using qRT-PCR just to check its stability and response under heavy metal stress. Results showed significant upregulation of the gene in the presence of Cd. It can be concluded that both Cd and Hg caused oxidative damage to plants, and adversely affected the quality of RNA. However, soybean tried to limit the adverse impacts of Cd and Hg stress by elevating the antioxidant system and upregulating Actin gene.