| Autor: |
Rae, Anne, Cybinski, Daisy, Jarmey, Janine, Smith, Frank |
| Zdroj: |
Plant Molecular Biology; September 2003, Vol. 53 Issue: 1-2 p27-36, 10p |
| Abstrakt: |
Putative phosphate transporters have been identified in a barley (Hordeum vulgareL.) genomic library by their homology to known phosphate transporters from dicot species. The genes designated HORvu;Pht1;1and HORvu;Pht1;6encode proteins of 521 and 535 amino acids respectively with 12 predicted membrane-spanning domains and other motifs common to the Pht1 family of phosphate transporters. HORvu;Pht1;1is expressed exclusively in roots and is strongly induced by phosphate deprivation. HORvu;Pht1;6is expressed in the aerial parts of the plant with strongest expression in old leaves and flag leaves. In situhybridization showed that HORvu;Pht1;6is expressed in the phloem of vascular bundles in leaves and ears. In order to study the biochemical properties of HORvu;Pht1;1 and HORvu;Pht1;6, the genes were expressed in transgenic rice (Oryza sativaL.) plants under the control of the rice actin promoter and suspension cell cultures were generated. Cells derived from transgenic plants were able to take up phosphate at a much higher rate than control cells, demonstrating that both genes encode functional phosphate transporters. The estimated Kmfor phosphate for cells expressing HORvu;Pht1;1was 9.06±0.82 μM, which is characteristic of a high-affinity transporter. The rate of phosphate uptake decreased with increasing pH, suggesting that HORvu;Pht1;1 operates as a H+/H2PO4−symporter. In contrast, the estimated Kmfor phosphate for cells expressing HORvu;Pht1;6was 385±61 μM, which is characteristic of a low-affinity transporter. Taken together, the results suggest that HORvu;Pht1;1 functions in uptake of phosphate at the root surface, while HORvu;Pht1;6 probably functions in remobilization of stored phosphate from leaves. |
| Databáze: |
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