THE CLONING OF 2 ARABIDOPSIS GENES BELONGING TO A PHOSPHATE TRANSPORTER FAMILY

Two genes, APT1 and APT2, with DNA sequences that exhibit significant sequence identity to yeast and fungal H+/orthophosphate co-transporter s, have been isolated from Arabidopsis thaliana. These genes are genet ically linked and map to chromosome 5 between markers g4028 and m435. The genes encode almost identical 524 amino acid polypeptides and are predicted to contain 12 membrane-spanning domains. Both APT1 and APT2 are predominantly expressed in A. thaliana root tissues. The level of expression of both genes in roots is regulated by the phosphorus statu s of the plant, being considerably enhanced when the plants were depri ved of an external phosphate supply. The APT1 and APT2 polypeptides ar e likely to be associated with the membrane transport of phosphate wit hin A. thaliana roots.