PHOSPHATE TRANSPORTERS FROM THE HIGHER-PLANT ARABIDOPSIS-THALIANA

Two cDNAs (AtPT1 and AtPT2) encoding plant phosphate transporters have been isolated from a library prepared with mRNA extracted from phosph ate-starved Arabidopsis thaliana roots, The encoded polypeptides are 7 8% identical to each other and show high degree of amino acid sequence similarity with high-affinity phosphate transporters of Saccharomyces cerevisiae, Neurospora crassa, and the mycorrhizal fungus Glomus vers iforme. The AtPT1 and AtPT2 polypeptides are integral membrane protein s predicted to contain 12 membrane-spanning domains separated into two groups of six by a large charged hydrophilic region, Upon expression, both AtPT1 and AtPT2 were able to complement the pho84 mutant phenoty pe of yeast strain NS219 lacking the high-affinity phosphate transport activity, AtPT1 and AtPT2 are representatives of two distinct, small gene families in A. thaliana. The transcripts of both genes are expres sed in roots and are not detectable in leaves. The steady-state level of their mRNAs increases in response to phosphate starvation.