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 photosynthetic energy conversion. Organic S compounds are subsequently synthesized in plants and made accessible to animals, primarily as the amino acid methionine. Thus, plant S metabolism clearly has nutritional importance in the global food chain. S metabolites may be part of redox regulation and drivers of essential metabolic pathways as cofactors and prosthetic groups, such as Fe-S centers, CoA, thiamine, and lipoic acid. The evolution of the S metabolic pathways and enzymes reflects the critical importance of functional innovation and diversifications. Here we review the major evolutionary alterations that took place in S metabolism across different scales and outline research directions that may take advantage of understanding the evolutionary adaptations.