Role of Sulfur Metabolism in Cadmium Tolerance

Abstract Heavy metal–contaminated soils pose a major environmental challenge. Plants uptake various nutrients and solutes from soil for their proper growth and development. The inadvertent uptake of toxic metals can affect plant metabolism, cell structure, transport, and membranes. Cadmium (Cd) is one of the most deleterious soil pollutants and is widely spread in the environment. Cd is phytotoxic, causing plant growth inhibition, stunting, and chlorosis due to altered plant metabolism. Sulfur (S) is an indispensable nutrient for plant growth and physiological functioning. S has a significant role in resistance against various biotic and abiotic stresses. Cd induces oxidative stress that affects the regulation of the S uptake and assimilation process at biochemical and genetic levels. S is incorporated in bioorganic compounds as reduced S in the form of organic sulfide or thiol, which provides protection against heavy metal stress through the synthesis of glucosinolates, allyl sulfur compounds, specialized peptides such as glutathione and phytochelatins, etc. This chapter provides information on the regulation of S metabolism and resistance mechanisms during Cd phytotoxicity.