Using an amphidiploid species to study sulfate transporter regulation

Plant sulfate uptake and systemic distribution are processes mediated by specific transporters whose activity is finely tuned to control sulfur fluxes in the plants depending on their metabolic needs, and their sulfur nutritional status. Cd exposure deeply affects sulfur metabolism and increases the root capability to take up sulfate, as a consequence of the increased plant sulfur needs depending on phytochelatin biosynthesis. Such a behavior is similar to that of sulfur starved plants, although in this case the increased capability to take up sulfate does not derive from increased plant sulfur needs but from the need to maintain the homeostasis of sulfur fluxes along the assimilatory pathway. Both the responses are mainly controlled at transcriptional level and have often been indicated as resulting from the same, although controversial, nutritional signal. We think that the use of amphidiploid species in the transcriptional control studies of sulfate transporters could be useful in order to underline possible multi-signalling regulatory pathways. In fact, the complexity of the amphidiploid genome, mainly concerning the existence of duplicated genes, may have led to the accumulation of mutations, which otherwise would have been eliminated by natural selection, that could give precious information on the transcriptional regulation mechanisms. Here we discuss the possibility that Cd and sulfur starvation modulate the expression of a high affinity sulfate transporter of Brassica juncea, an amphidiploid species carrying both the chromosomal sets of the ancestral parents Brassica nigra and Brassica campestris, through independent and partially overlapping signals