Uptake, Distribution and Subcellular Transport of Sulfate

Abstract

Sulfate transport in and out of the cell in all phototrophic organisms, and in addition in eukaryotes, influx and efflux from the vacuole, which acts as a cellular sulfate store, and into the plastid, the site of sulfate reduction, is facilitated by multiple transporters. In addition, in vascular plants these transport processes are coordinated to facilitate management of sulfur fluxes between organs, from roots to shoots and to generative tissues. In prokaryotes, uptake into the cell is driven predominantly by an ABC-transporter, which is the product of at least four genes and energized directly by ATP. In eukaryotes, a family of H+-sulfate co-transporters (SulP) has been characterized which fulfills transport roles at least for uptake into the cell and efflux from the vacuole. In addition, differential expression of this gene family in vascular plants enables selective movement between tissues dependent on developmental cues and sulfate availability. A vital transport step is the transport into the plastid, for which a transporter has only been identified in algae and for which no vascular plant homologue is known. The expression of many sulfate transporters responds to availability and demand for sulfur, and transduction mechanisms which control this are beginning to be elucidated. The significance of a C-terminal STAS domain in SulP transporters is still unclear.