Role of Zinc Homeostasis in Plant Growth

Abstract

Zinc is one of the most important micronutrients required for optimal plant growth and productivity. Paradoxically, a higher concentration of the same can be toxic for the plants, and hence, a constant supply of zinc to maintain an optimal intracellular concentration in plants is required which is referred to as zinc homeostasis. Homeostasis also includes subcellular distribution of zinc and its vesicular storage. To maintain this optimal intracellular concentration, plant cell uses a number of biochemical mechanisms involving a tightly regulated network of dozens of intracellular proteins. Membrane of transport proteins, cation transporters, cation diffusion facilitator, Zn-binding proteins, ligands, members of ZIP family, and metal tolerance proteins are some constituting members of this network. Emerging evidences suggest that these networks of proteins are conserved among land plants. In addition to maintaining the intracellular concentration of zinc, this network coordinates processes like sequestration, zinc uptake from soil, and its transport in the plant ensuring adequate zinc supply to all the cells in the plants. The metal homeostasis network exhibits plasticity to respond to variations in bioavailable soil metal. Due to the chemical similarity between zinc and other divalent cations like iron and cadmium, these metals serve as zinc mimic. The presence of these metals along with zinc therefore affects zinc homeostasis and results in accumulation of unwanted metals in food grains.