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Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
Published on: September 28, 2018
Kinetics of Membrane Transport during Chloroplast Development
1Institut für Botanik, Technische Universität München, Arcisstrasse 21, D-8000 München 2, West Germany.
Plant Physiology
|November 1, 1978
Summary
Early plastids have specific transporters for phosphate and dicarboxylic acids. Changes in transport rates during development are due to altered transport velocity, not affinity, suggesting a distinct early phosphate transport mechanism.
Area of Science:
- Plant Biology
- Cell Biology
- Biochemistry
Background:
- Plastid development involves dynamic changes in envelope membrane permeability.
- Understanding metabolite transport is crucial for plant growth and photosynthesis.
Purpose of the Study:
- To investigate the kinetics of membrane transport during etioplast to chloroplast development in Avena sativa.
- To identify specific transporters involved in early plastid development and their functional changes.
Main Methods:
- Utilized uncontaminated and intact etioplast/etiochloroplast preparations from greening Avena sativa laminae.
- Analyzed transport kinetics, including competitive inhibition, to characterize transporter function and affinity (K(m)).
Main Results:
- Etioplasts possess specific translocators for orthophosphate, dihydroxyacetone phosphate, 3-phosphoglycerate (phosphate translocator), and dicarboxylic acids (dicarboxylate translocator).
- Uptake rate changes during development are primarily driven by altered transport velocity, not changes in affinity or nonspecific permeation.
- Early developmental stages (up to 3 hours illumination) show low competitive inhibition, suggesting a distinct early phosphate transport mechanism.
Conclusions:
- Etioplasts exhibit specific and regulated transport systems for key metabolites.
- The velocity of transport, rather than affinity, is the main regulatory factor for metabolite uptake during early plastid development.
- A unique phosphate transport mechanism may operate in early plastids, differing from that in more mature ones.
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