Distribution of Pht1 genes ( LePT1 to 8 and StPT1 to 10) on the tomato (T) and potato (P) chromosomes. Chromosome numbers are shown at the top of each bar. The arrows next to the gene names indicate the direction of transcription. LePTx, StPTx1 and StPTx2 are putative Pht1 pseudogenes residual in the tomato and potato genomes. The genes from other two families, Pht3 and Pht4, encoding putative Pi transporter or carrier with no homology to the Pht1 proteins, were also labeled on the corresponding chromosomes of the two plants.