Sulfate Transport and Assimilation in Plants1

Abstract

Sulfur is one of the six macronutrients required by plants and is found in the amino acids Cys and Met and in a variety of metabolites. When one considers that sulfur in plants is only 3% to 5% as abundant as nitrogen, it is perhaps understandable that sulfur assimilation has been less well studied. As a part of the Cys molecule, the sulfur group, called a thiol, is strongly nucleophilic (electron-donating), making it ideally suited for biological redox processes. When oxidized, two Cys molecules can form a covalent linkage called a disulfide bond, which is readily broken by reduction to form two thiol groups. Disulfide ↔ dithiol interchange is so versatile that nearly all aerobic forms of life, including plants, have evolved to use this reaction as the dominant form of redox control. Redox control regulates enzymes and protects against oxidative damage.