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Evidence for amino-acid: proton cotransport in Ricinus cotyledons
1Biology Department, University of California, 95064, Santa Cruz, CA, USA.
Planta
|December 5, 2013
Summary
Castor bean cotyledons absorb amino acids via proton cotransport, a process vital for seedling growth. This transport mechanism is energy-dependent and involves specific carriers for amino acids and sucrose.
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- During castor bean germination, proteins are hydrolyzed, and amino acids are transferred to cotyledons for seedling development.
- Castor bean cotyledons actively absorb amino acids, even after removal of the endosperm and hypocotyl.
Purpose of the Study:
- To investigate the mechanism of amino acid and sucrose transport in castor bean cotyledons.
- To determine the role of proton cotransport in nutrient uptake.
Main Methods:
- Measurement of amino acid uptake rates in castor bean cotyledons.
- Analysis of pH changes in the external medium induced by L-glutamine and sucrose.
- Use of respiration inhibitors and uncouplers to assess energy dependence.
Main Results:
- L-glutamine uptake was inhibited by high KCl concentrations, suggesting a role for membrane potential.
- L-glutamine and other amino acids induced a proton uptake, proportional to their transport rate.
- Sucrose also induced proton uptake, indicating a shared proton cotransport system with separate carriers for amino acids and sucrose.
Conclusions:
- Amino acid and sucrose transport in castor bean cotyledons occur via proton cotransport.
- The transport systems for amino acids and sucrose involve distinct carriers within the same membrane system.
- This mechanism is crucial for nutrient translocation during early seedling development.
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