Nitric Oxide Signaling During Cadmium Stress Induced Programmed Cell Death in Pea

Abstract

newline Cadmium, a non-essential heavy metal is highly toxic to living organisms including plants. It has harmful effect on the growth, development and metabolism of plants. Cd at high concentrations promotes ROS bursts which cause lipid peroxidation, protein oxidation and DNA damage leading to cell death in plants. Plants possess antioxidant defense system to combat the danger posed by ROS. Under severe Cd stress condition, however, the antioxidant capacity of plants may not be adequate to reduce the harmful effect of oxidative injury. Nitric oxide (NO) a small, universal bioactive molecule plays a significant role in stress signaling and various physiological processes in plants. Therefore, the present study was undertaken with the objective to study ameliorating effect of nitric oxide donated by SNP on Cd induced stress and programmed cell death in pea (Pisum sativum L.) seedlings. The increase in the concentration of Cd, reduced germination of seeds, growth of germinating pea seedlings and increased proline content suggesting a possible toxic effect of this heavy metal on germination of pea seeds. When different concentrations of SNP were supplied with 50 and 200 and#956;M CdCl2, 50 and#956;M SNP was found to be optimum in alleviating the inhibitory effects caused by Cd and partially reversed the damage caused by the Cd as shown by increased seed germination, seedling vigour, fresh weight, dry weight and decreased proline content in germinating pea seedlings. It also reduced H2O2 accumulation, malondialdehyde content and increased endogenous NO content, NR activity, total phenols and flavonoids content, catalase and peroxidase activity in pea seedlings. DNA laddering which appeared in 50 and 200 and#956;M CdCl2 treated seedlings was weakened in seedlings treated with 50 and#956;M SNP along with 50 and 200 and#956;M CdCl2.