Transcriptional regulation of plant phosphate transporters

Phosphorus is acquired by plant roots primarily via the high-affinity inorganic phosphate (P(i)) transporters. The transcripts for P(i) transporters are highly inducible upon P(i) starvation, which also results in enhanced P(i) uptake when P(i) is resupplied. Using antibodies specific to one of the tomato P(i) transporters (encoded by LePT1), we show that an increase in the LePT1 transcript under P(i) starvation leads to a concurrent increase in the transporter protein, suggesting a transcriptional regulation for P(i) acquisition. LePT1 protein accumulates rapidly in tomato roots in response to P(i) starvation. The level of transporter protein accumulation depends on the P(i) concentration in the medium, and it is reversible upon resupply of P(i). LePT1 protein accumulates all along the roots under P(i) starvation and is localized primarily in the plasma membranes. These results clearly demonstrate that plants increase their capacity for P(i) uptake during P(i) starvation by synthesis of additional transporter molecules.