Calystegines in potatoes with genetically engineered carbohydrate metabolism
Ute Richter1, Uwe Sonnewald, Birgit Dräger
1Department of Pharmacy, Faculty of Science I Biosciences, Martin Luther University Halle-Wittenberg, Hoher Weg 8, D-06120 Halle, Germany.
Journal of Experimental Botany
|April 14, 2007
Summary
Calystegine accumulation in potato tubers is influenced by genetic modifications affecting carbohydrate metabolism. Enhanced soluble sugars, particularly sucrose, correlate with increased calystegine levels, primarily synthesized in roots.
Area of Science:
- Plant biochemistry
- Metabolomics
- Alkaloid biosynthesis
Background:
- Calystegines are nortropane alkaloids with glycosidase inhibitory properties found in various vegetables.
- Previous studies suggested carbohydrate availability influences calystegine accumulation in root cultures.
- The relationship between carbohydrate metabolism and calystegine levels in planta, especially in model plants like potato, remained unclear.
Purpose of the Study:
- To investigate the link between genetic modifications in carbohydrate metabolism and calystegine accumulation in potato tubers.
- To determine the origin of calystegines in tubers and their response to altered sugar levels.
- To correlate calystegine biosynthesis gene expression and enzyme activity with product accumulation under varying carbohydrate conditions.
Main Methods:
- Analysis of transgenic potato lines with altered carbohydrate metabolism (overexpression of yeast invertase, antisense suppression of sucrose synthase).
- Quantification of calystegine levels in tubers and other plant organs (roots, stolons).
- Measurement of transcripts and enzyme activities related to calystegine biosynthesis.
Main Results:
- Potato tubers with increased soluble sugars (via yeast invertase or suppressed sucrose synthase) showed elevated calystegine levels.
- Calystegines in tubers are primarily synthesized in roots, but tuber levels are responsive to tuber carbohydrate status.
- The strongest calystegine increase was observed in tubers with suppressed sucrose synthase activity.
- Enhanced soluble sugars in roots and stolons also correlated with higher calystegines and related enzyme activities.
Conclusions:
- Calystegine accumulation in potato tubers is significantly influenced by genetic alterations in carbohydrate metabolism.
- Sucrose availability appears to be a key factor regulating calystegine levels, with increased sucrose promoting accumulation.
- While root biosynthesis is dominant, tuber carbohydrate status plays a crucial role in modulating overall calystegine levels in the plant.
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