A higher plant homologue to the high-affinity phosphate transporter gene of yeast (Saccharomyces cerevisiae) PHO84 was isolated from Arabidopsis thaliana. Expression of the Arabidopsis gene PHT1 at high levels in tobacco-cultured cells increased the rate of phosphate uptake. The uptake activity attributable to the transgene was inhibited by protonophores, suggesting an H+ cotransport mechanism of phosphate uptake, and had a Km of 3.1 microM which is within limits characteristic of high-affinity transport mechanisms. These results indicate that PHT1 encodes a high-affinity phosphate transporter. The transgenic cells exhibited increased biomass production when the supply of phosphate was limited, establishing gene engineering of phosphate transport as one approach toward enhancing plant cell growth.