PCP: Phosphate and crop productivity

• Research unit: EU RFP
• Project number: 96.0023-2

Key words (English)

Arabidopsis; mutant; phosphate; transport; roots

Alternative project number (English)

EU project number: BIO4CT960770

Research programs (English)

EU-programme: 4. Frame Research Programme - 4.1 Biotechnology

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise:
Université de Lausanne
Institut de Biologie et de Physiologie végétale

Partners and International Organizations (English)

Coordinator: MPI-MOPP (D)

Abstract (English)

Loading of inorganic phosphate (Pi) from root tissue into the xylem is strongly reduced in the Arabidopsis thaliana mutant phol. The aim of this work was to isolate the wild type PHO1 gene by means of map-based cloning and further characterization of the gene function. The PHO1 locus was initially map to the upper arm of chromosome three. After an extensive phase of YAC and BAC isolation, creation of new markers and fine mapping, a region of approximately 100 kb was identified covering the PHO1 locus. Based on the sequence of this region obtained through the Arabidopsis sequencing project, a putative gene was identified. Transformation of the pho1 mutant with a genomic fragment containing this gene complemented the Pi deficiency phenotype, proving that PHO1 had been cloned. Sequence analysis of four mutant alleles available in our lab provided additional confirmation of the successfull cloning of PHO1. Further, the sequences of these alleles revealed that they were leading to shortened truncated version of the PHOl protein. The deduced amino acid sequence of the PHOl protein shows the structure expected for a solute transporter. The hydropathy profile of PHOl reveals that the N-terminal half is mainly hydrophilic while the C-terminal half has alternating stretches of hydrophilic and hydrophobic regions, a pattem which is typical of membrane-spanning domains. But it does not show significant homologies to characterised solute transporter in any organisms, including plants. However, homologies are found within the Arabidopsis genome with 6 other genes. Expression of PHO1 was analysed by Northern and PHOl-promotor-GUS fusions. The gene is mainly transcribed in roots and only slightly modulated by Pi (about 2 fold). GUS staining is most prominent in the vascular system of the root and the root tip is not stained. GUS staining is also present in the vascular system of the hypocotyl. These expression patterns of PHO1 (Northern and GUS) fit very well with its role in Pi loading in the xylem. Preliminary analysis of the promoter-GUS fusion of the identified PHOl homologues showed that for some an expression pattern distinct from PHO1 can be observed. Finally, the PHO1 protein can be expressed in Xenopus oocytes and yeast, thus enabling the use of these heterologous system to analyse to mode of action of PHO1.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0023-2