Phosphate and crop productivity

Project Information

Grant agreement ID: BIO4960770

Project closed

Start date 1 December 1996

End date 29 February 2000

Funded under

• Specific research, technological development and demonstration programme in the field of biotechnology, 1994-1998

Total cost

No data

EU contribution

No data

Coordinated by

MAX-PLANCK-GESELLSCHAFT ZUR FOERDERUNG DER WISSENSCHAFTEN E.V.
Germany

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Deliverables

Identification of the PHO1 gene of Arabidopsis involved in the loading of phosphate to the xylem

Inorganic phosphate (Pi) is one of the most limiting nutrients for plant growth. In order to acquire and distribute Pi across the whole plants, ions must be transported first into the cells of the root to be then exported into the xylem vessels for ion delivery to the shoot. Pi loading into the xylem of the root is thus an important step for the plant Pi utilization. We have cloned a gene from the plant Arabidopsis, named PHO1, involved in the loading of Pi into the xylem of the root. The protein shows typical features of solute transporters, such as the presence of several membrane-spanning domains. However, PHO1 does not show any homology to characterised transporters, including the cloned Pi transporters of plants, bacteria, fungi and animals. The expression pattern of the gene confirms its involvement in Pi loading to the xylem since the gene is mainly expressed in the cells of the stele of roots. Heterologous expression of PHO1 in yeast and Xenopus oocytes have failed to confirm that PHO1 is itself the transporter involved in the exit of Pi out of cells. Furthermore, overexpression of the gene in Arabidopsis has so far failed to reveal a difference in Pi transport activity. It is possible that PHO1 may be just one component of a multimeric transporter, or that it is indirectly involved in regulating the activity of another Pi Transporter. A total of 9 PHO1 homologues have been detected in the Arabidopsis genome, indicating the presence of a family of proteins involved in Pi transport. Preliminary evidence indicated that the other genes have distinct expression patterns, implying their involvement in global Pi homeostasis. We have cloned a gene from the plant Arabidopsis, named PHO1, involved in the loading of Pi into the xylem of the root. The protein shows typical features of solute transporters, such as the presence of several membrane-spanning domains. However, PHO1 does not show any homology to characterised transporters, including the cloned Pi transporters of plants, bacteria, fungi and animals. The expression pattern of the gene confirms its involvement in Pi loading to the xylem since the gene is mainly expressed in the cells of the stele of roots. Heterologous expression of PHO1 in yeast and Xenopus oocytes have failed to confirm that PHO1 is itself the transporter involved in the exit of Pi out of cells. Furthermore, over-expression of the gene in Arabidopsis has so far failed to reveal a difference in Pi transport activity. It is possible that PHO1 may be just one component of a multimeric transporter, or that it is indirectly involved in regulating the activity of another Pi transporter. A total of 9 PHO1 homologues have been detected in the Arabidopsis genome, indicating the presence of a family of proteins involved in Pi transport. Preliminary evidence indicates that the other genes have distinct expression patterns, implying their involvement in global Pi homeostasis.