Transcriptional regulation of plant phosphate transporters.

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