Adaptive Modifications in Plant Sulfur Metabolism over Evolutionary Time.

Sulfur (S) is an essential element for life on Earth. Plants are able to take up and utilize sulfate (SO42-), the most oxidized inorganic form of S compounds on Earth, through the reductive S assimilatory pathway that couples with the photosynthetic energy conversion. Organic S compounds are subsequently synthesized in plants and made accessible to animals, primarily as the amino acid methionine. Thus, the plant S metabolism clearly has nutritional importance in the global food chain. The S metabolites may be part of the redox regulation and drivers of essential metabolic pathways as cofactors and prosthetic groups, such as Fe-S centers, coenzyme A, thiamine, and lipoic acid. The evolution of the S metabolic pathways and enzymes reflects critical importance of the functional innovation and diversifications. Here we review the major evolutionary alterations that took place in the S metabolism across different scales and outline research directions that may take advantage of understanding the evolutionary adaptations.