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Sugar Levels Modulate Differential Expression of Maize Sucrose Synthase Genes.
K. E. Koch1, K. D. Nolte, E. R. Duke
1Fruit Crops Department, University of Florida, Gainesville, Florida 32611.
The Plant Cell
|January 1, 1992
Summary
Maize sucrose synthase genes Sh1 and Sus1 respond differently to sugar levels. Sh1 is active with low sugars, while Sus1 requires high sugar availability for expression.
Area of Science:
- Plant Molecular Biology
- Plant Physiology
- Biochemistry
Background:
- Sucrose synthase is crucial for sucrose metabolism in developing plant organs.
- Maize possesses two sucrose synthase genes, Sh1 and Sus1, with distinct roles.
Purpose of the Study:
- To investigate the differential regulation of maize Sh1 and Sus1 genes by carbohydrate availability.
- To understand how sugar levels influence sucrose synthase gene expression, protein localization, and enzyme activity.
Main Methods:
- Excised maize root tips were incubated with varying concentrations of different sugars.
- Gene expression (mRNA levels) and protein abundance were analyzed.
- Cellular localization of sucrose synthase protein was examined using microscopy.
Main Results:
- Sh1 mRNA expression peaked under low glucose conditions (~0.2%), while Sus1 mRNA levels increased significantly with higher glucose concentrations (2.0%).
- Protein abundance changes mirrored mRNA trends but were less pronounced.
- Total enzyme activity remained unchanged, but cellular localization of sucrose synthase shifted based on sugar availability.
Conclusions:
- Differential regulation of Sh1 and Sus1 by sugar levels provides a mechanism to control sucrose synthase distribution and activity in maize roots.
- This regulation allows plants to adapt sucrose metabolism to varying carbohydrate status and photosynthetic supply.