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Functional analysis and cell-specific expression of a phosphate transporter from tomato
P Daram1, S Brunner, B L Persson
1Federal Institute of Technology (ETH) Zurich, Institute of Plant Sciences, Lindau, Switzerland.
Planta
|September 16, 1998
Summary
Researchers identified a tomato phosphate transporter (LePT1) crucial for nutrient uptake. This protein functions in specific root cells, enhancing phosphate acquisition at the root-soil interface, even under low nutrient conditions.
Area of Science:
- Plant Molecular Biology
- Plant Physiology
- Biochemistry
Background:
- Understanding orthophosphate (Pi) uptake is vital for plant nutrition and agricultural productivity.
- The root/soil interface is a critical zone for nutrient acquisition.
- Phosphate transporters play a key role in mediating Pi uptake across cell membranes.
Purpose of the Study:
- To clone and characterize a novel phosphate transporter cDNA (LePT1) from tomato (Lycopersicon esculentum Mill.).
- To investigate the molecular and biochemical properties of the LePT1 protein.
- To determine the expression pattern and localization of LePT1 in tomato roots.
Main Methods:
- Cloning of LePT1 cDNA from a tomato root air-specific cDNA library.
- Expression of LePT1 in a Pi-uptake-deficient yeast mutant to assess functionality.
- Biochemical characterization of LePT1 activity, including Km determination and pH optimum.
- Analysis of LePT1 transcript levels using quantitative PCR and in situ hybridization.
Main Results:
- The cloned LePT1 encodes a protein with twelve putative transmembrane domains, homologous to known Pi transporters.
- Expressed LePT1 in yeast showed an apparent Km of 31 µM and was active at submicromolar Pi concentrations.
- LePT1-mediated Pi uptake was highest at pH 5 and dependent on the electrochemical membrane potential.
- LePT1 transcripts were detected in all vegetative organs, with highest levels in root hairs.
- In situ hybridization revealed cell-specific LePT1 expression in rhizodermal and root cap cells, and in young stelar tissue under Pi deprivation.
Conclusions:
- LePT1 is a functional phosphate transporter in tomato with significant activity at low Pi concentrations and acidic pH.
- The study provides molecular and biochemical evidence for the role of LePT1 in Pi acquisition at the root/soil interface.
- Distinct root cell types, particularly peripheral cells, play a crucial role in phosphate uptake, mediated by transporters like LePT1.