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Plasma membrane vesicles from source and sink leaves : changes in solute transport and polypeptide composition
R Lemoine1, O Gallet, C Gaillard
1Laboratoire de Physiologie et Biochimie Végétales, Unité Associée Centre National de la Recherche Scientifique 574, Université de Poitiers, 25 rue du Faubourg Saint-Cyprien, 86000 Poitiers, France.
Plant Physiology
|November 1, 1992
Summary
Plasma membrane vesicles (PMVs) from sugar beet source leaves accumulate significantly more sucrose than those from sink leaves. This difference is linked to proton-sucrose cotransporter activity and abundance in source leaves.
Area of Science:
- Plant Physiology
- Molecular Biology
- Biochemistry
Background:
- Sugar beet leaf development involves a transition from source to sink tissues.
- Plasma membrane vesicles (PMVs) are crucial for studying transport mechanisms.
- Understanding sucrose transport is vital for plant productivity.
Purpose of the Study:
- To investigate differences in sucrose uptake between PMVs from sugar beet source and sink leaves.
- To identify the molecular mechanisms underlying sucrose accumulation differences.
- To explore the role of proton-sucrose cotransport in leaf development.
Main Methods:
- Preparation of PMVs from sugar beet source and sink leaves using phase partitioning.
- Measurement of sucrose, glucose, and valine uptake under imposed proton motive force.
- Inhibition studies using N-ethylmaleimide and antibodies against a 42-kD protein.
- Analysis of protein abundance using SDS-PAGE and Western blot.
Main Results:
- PMVs from source leaves showed a 4-fold higher sucrose accumulation than sink leaf PMVs.
- Glucose and valine uptake were unaffected by developmental stage.
- Sucrose uptake in source leaf PMVs was inhibited by N-ethylmaleimide and specific antibodies.
- A 42-kD polypeptide, potentially a sucrose carrier, was more abundant in source leaf PMVs.
Conclusions:
- The sink/source transition in sugar beet leaves involves the incorporation or activation of proton-sucrose cotransporter proteins in the plasma membrane.
- A 42-kD polypeptide is likely involved in mediating proton-sucrose cotransport and is more prevalent in source leaves.
- These findings elucidate key mechanisms of sugar transport during plant development.
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