title: Molecular cloning, characterization and expression analysis of two members of the Pht1 family of phosphate transporters in Glycine max.
abstract: BACKGROUND
  Phosphorus is one of the macronutrients essential for plant growth and development. The acquisition and translocation of phosphate are pivotal processes of plant growth. In a large number of plants, phosphate uptake by roots and translocation within the plant are presumed to occur via a phosphate/proton cotransport mechanism.
  
  
  RESULTS
  We cloned two cDNAs from soybean (Glycine max), GmPT1 and GmPT2, which show homology to the phosphate/proton cotransporter PHO84 from the budding yeast Saccharomyces cerevisiae. The amino acid sequence of the products predicted from GmPT1 and GmPT2 share 61% and 63% identity, respectively, with the PHO84 in amino acid sequence. The deduced structure of the encoded proteins revealed 12 membrane-spanning domains with a central hydrophilic region. The molecular mass values are ∼58.7 kDa for GmPT1 and ∼58.6 kDa for GmPT2. Transiently expressed GFP-protein fusions provide direct evidence that the two Pi transporters are located in the plasma membrane. Uptake of radioactive orthophosphate by the yeast mutant MB192 showed that GmPT1 and GmPT2 are dependent on pH and uptake is reduced by the addition of uncouplers of oxidative phosphorylation. The K(m) for phosphate uptake by GmPT1 and GmPT2 is 6.65 mM and 6.63 mM, respectively. A quantitative real time RT-PCR assay indicated that these two genes are expressed in the roots and shoots of seedlings whether they are phosphate-deficient or not. Deficiency of phosphorus caused a slight change of the expression levels of GmPT1 and GmPT2.
  
  
  CONCLUSIONS
  The results of our experiments show that the two phosphate transporters have low affinity and the corresponding genes are constitutively expressed. Thereby, the two phosphate transporters can perform translocation of phosphate within the plant.
authors.affiliation: National Center for Soybean Improvement, National Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, Jiangsu, China.
authors.forename: Zhaoyun
authors.initials: Z
authors.lastname: Wu
authors.forename: Jinming
authors.initials: J
authors.lastname: Zhao
authors.forename: Ruifang
authors.initials: R
authors.lastname: Gao
authors.forename: Guanjun
authors.initials: G
authors.lastname: Hu
authors.forename: Junyi
authors.initials: J
authors.lastname: Gai
authors.forename: Guohua
authors.initials: G
authors.lastname: Xu
authors.forename: Han
authors.initials: H
authors.lastname: Xing
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D028061:Phosphate Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D028061:Phosphate Transport Proteins; D010940:Plant Proteins