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Sucrose metabolism in plastids.
N Gerrits1, S C Turk, K P van Dun
1Department of Molecular Plant Physiology and Molecular Cell Biology, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Plant Physiology
|February 13, 2001
Summary
Sucrose can efficiently enter plant plastids, challenging previous assumptions. Experiments using introduced enzymes demonstrate significant sucrose metabolism within chloroplasts and amyloplasts, suggesting a novel role for sucrose in these organelles.
Area of Science:
- Plant Biology
- Molecular Biology
- Biochemistry
Background:
- The presence and role of sucrose (Suc) within plant plastids, such as chloroplasts and amyloplasts, remain a subject of debate.
- Previous reports of low sucrose levels in isolated chloroplasts were often attributed to experimental artifacts.
Purpose of the Study:
- To investigate the potential for substantial sucrose entry into plant plastids.
- To explore the metabolic fate and functional implications of sucrose within these organelles.
Main Methods:
- Genetically engineered tobacco and potato plants by targeting sucrose-metabolizing enzymes, levansucrase and invertase, to plastids.
- Quantified fructan accumulation and sucrose content to assess enzyme activity and sucrose transport.
Main Results:
- Targeting levansucrase to plastids resulted in high-level fructan accumulation in chloroplasts and amyloplasts.
- Introduction of levansucrase into amyloplasts led to significant alterations in starch structure.
- Expression of yeast invertase in potato amyloplasts caused an 80% reduction in total sucrose content, indicating efficient sucrose hydrolysis.
Conclusions:
- These findings strongly suggest that sucrose can efficiently enter plant plastids.
- The results open new avenues for research into the function and metabolism of sucrose within plastids.
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