Plant Metallothioneins

The maintenance of ion homeostasis in plant cells is a fundamental physiological requirement for sustainable plant growth, development, and production. Metallothioneins (MTs) are a superfamily of cysteine-rich, low-molecular-weight metalloproteins that bind heavy metal ions. These cytosolic metallopeptides are widely distributed in living organisms and are thought to be involved in metal homeostasis, metal detoxification, and oxidative stress protection. Plants produce these metal-chelating proteins to overcome the toxic effects of heavy metals and were predominantly found to be expressed in leaves, roots, and callus. Similarly, phytochelatins (PCs) are sulfur-rich metal-binding peptides, and PC synthesis is one of the key mechanisms by which plants protect themselves against metal toxicity by binding complexes with high-affinity ligands in the vacuole, thereby keeping the released toxins away from the metal-sensitive metabolic centers in the cytoplasm. Genetic engineering has been established to enhance the plant’s ability to endure and mitigate the environmental stress. Several transgenic approaches have been carried out successfully that provide a lot of scope in understanding the mechanism of heavy metal uptake as well as plants ability to withstand the environmental stresses. This chapter briefly summarizes the classification, distribution, and various aspects of functional as well as regulatory mechanism of MTs.