Metal transporters in organelles and their roles in heavy metal transportation and sequestration mechanisms in plants

Heavy metal toxicity is one of the major concerns for agriculture and health. Accumulation of toxic heavy metals at high concentrations in edible parts of crop plants is the primary cause of disease in humans and cattle. A dramatic increase in industrialization, urbanization, and other high anthropogenic activities has led to the accumulation of heavy metals in agricultural soil, which has consequently disrupted soil conditions and affected crop yield. By now, plants have developed several mechanisms to cope with heavy metal stress. However, not all plants are equally effective in dealing with the toxicity of high heavy metal concentrations. Plants have modified their anatomy, morphophysiology, and molecular networks to survive under changing environmental conditions. Heavy metal sequestration is one of the essential processes evolved by some plants to deal with heavy metals' toxic concentration. Some plants even have the ability to accumulate metals in high quantities in the shoots/organelles without toxic effects. For intercellular and interorganeller metal transport, plants harbor spatially distributed various transporters which mainly help in uptake, translocation, and redistribution of metals. This review discusses different heavy metal transporters in different organelles and their roles in metal sequestration and redistribution to help plants cope with heavy metal stress. A good understanding of the processes at stake helps in developing more tolerant crops without affecting their productivity.