Starch synthesis by isolated amyloplasts from wheat endosperm
1Botany School, University of Cambridge, Downing Street, CB2 3EA, Cambridge, UK.
Planta
|November 14, 2013
Summary
Glucose 1-phosphate is the primary compound that enters wheat grain amyloplasts for starch synthesis. This C-6 compound, not a C-3, provides the essential carbon for developing grains.
Area of Science:
- Plant Biochemistry
- Molecular Biology
- Agricultural Science
Background:
- Starch synthesis is crucial for grain development in Triticum aestivum (wheat).
- The specific carbon source entering amyloplasts for starch synthesis remains a key question in plant physiology.
Purpose of the Study:
- To identify the compound(s) that cross the amyloplast envelope to supply carbon for starch synthesis in wheat grains.
- To elucidate the mechanism of carbon transport into amyloplasts for starch production.
Main Methods:
- Isolation of amyloplasts from developing wheat endosperm protoplasts.
- Incubation of isolated amyloplasts with various 14C-labelled compounds, including glucose and its phosphorylated derivatives.
- Measurement of 14C incorporation into starch and analysis of the soluble fraction.
Main Results:
- Glucose 1-phosphate significantly labeled starch in an intact amyloplast-dependent manner.
- Starch labeling by glucose 1-phosphate was linear for 2 hours.
- Over 98% of the soluble 14C was recovered as glucose 1-phosphate, indicating minimal pre-uptake metabolism.
Conclusions:
- Glucose 1-phosphate is the likely compound entering wheat amyloplasts for starch synthesis.
- Evidence supports a C-6, rather than a C-3, compound as the carbon source for starch synthesis in wheat grains.
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