Pht2;1 encodes a low-affinity phosphate transporter from Arabidopsis

• Published in: The Plant cell Vol. 11; no. 11; pp. 2153 - 2166
• Main Authors: Daram, P, Brunner, S, Rausch, C, Steiner, C, Amrhein, N, Bucher, M
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Physiologists 01.11.1999; American Society of Plant Biologists
• Subjects: Amino Acid Sequence; amino acid sequences; Amino acids; Animals; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cloning, Molecular; Complementary DNA; Electrochemistry; exons; Gels; genbank/x98130; gene expression; gene transfer; genes; genetic transformation; Humans; introns; ion transport; Leaves; Messenger RNA; Models, Molecular; Molecular Sequence Data; nucleotide sequences; nutrient transport; Phosphate transport proteins; Phosphate-Binding Proteins; Phosphates; Phosphates - metabolism; Plant cells; plant proteins; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; plasma membrane; Protein Conformation; Rats; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; RNA; roots; Saccharomyces cerevisiae; Sequence Alignment; Sequence Homology, Amino Acid; shoots; Topology; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.11.11.2153

An Arabidopsis genomic sequence was recently shown to share similarity with bacterial and eukaryotic phosphate (Pi) transporters. We have cloned the corresponding cDNA, which we named Pht2;1, and subsequently performed gene expression studies and functional analysis of the protein product. The cDNA encodes a 61-kD protein with a putative topology of 12 transmembrane (TM) domains interrupted by a large hydrophilic loop between TM8 and TM9. Two boxes of eight and nine amino acids, located in the N- and C-terminal domains, respectively, are highly conserved among species across all kingdoms (eubacteria, archea, fungi, plants, and animals). The Pht2;1 gene is predominantly expressed in green tissue, the amount of transcript staying constant in leaves irrespective of the Pi status of the shoot; in roots, however, there is a marginal increase in mRNA amounts in response to Pi deprivation. Although the protein is highly similar to eukaryotic sodium-dependent Pi transporters, functional analysis of the Pht2;1 protein in mutant yeast cells indicates that it is a proton/Pi symporter dependent on the electrochemical gradient across the plasma membrane. Its fairly high apparent K(m) for Pi (0.4 mM) and high mRNA content in the shoot, especially in leaves, suggest a role for shoot organs in Pi loading. Pht2;1 thus differs from members of the recently described plant Pi transporter family in primary structure, affinity for Pi, and presumed function.