Molecular Defense Mechanisms in Plants to Tolerate Toxic Action of Heavy Metal Environmental Pollution

Abstract

Toxic action of heavy metals on plants growing in contaminated soils intensified the research on detoxification and sequestering mechanisms existing in plants to understand and manipulate defense mechanisms that confer tolerance against metal ions. Increased biosynthesis of plant biomolecules to confer tolerance during toxic action of heavy metals is an intrinsic ability of plants. Induced formation of low-molecular weight amino acids, peptides or proteines as chelators such as proline (Pro), glutathione (GSH), phytochelatins (PCs) or metallothioneins (MTs) under heavy metal stress enhances metal binding and detoxification capability of plants. In addition, proline and GSH related enzymes such as GSH reductase, GSH peroxidases and glutathione S-transferases are also key components of the antioxidant defense system in the cells to scavenge reactive oxygen species (ROS). Protective action of oxidized fatty acids oxylipins at toxic levels of heavy metals is considered to activate detoxification processes as signaling molecules.