Fructose 2,6-bisphosphate activates pyrophosphate: fructose-6-phosphate 1-phosphotransferase and increases triose phosphate to hexose phosphate cycling in heterotrophic cells |
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Authors: | Alisdair R Fernie Albrecht Roscher R George Ratcliffe Nicholas J Kruger |
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Institution: | (1) Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK, GB |
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Abstract: | The aim of this work was to establish the influence of fructose 2,6-bisphosphate (Fru-2,6-P2) on non-photosynthetic carbohydrate metabolism in plants. Heterotrophic callus lines exhibiting elevated levels of Fru-2,6-P2 were generated from transgenic tobacco (Nicotiana tabacum L.) plants expressing a modified rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Lines containing increased
amounts of Fru-2,6-P2 had lower levels of hexose phosphates and higher levels of 3-phosphoglycerate than the untransformed control cultures. There
was also a greater redistribution of label into the C6 position of sucrose and fructose, following incubation with 1-13C]glucose, in the lines possessing the highest amounts of Fru-2,6-P2, indicating a greater re-synthesis of hexose phosphates from triose phosphates in these lines. Despite these changes, there
were no marked differences between lines in the metabolism of 14C-substrates, the rate of oxygen uptake, carbohydrate accumulation or nucleotide pool sizes. These data provide direct evidence
that physiologically relevant changes in the level of Fru-2,6-P2 can affect pyrophosphate: fructose-6-phosphate 1-phosphotransferase (PFP) activity in vivo, and are consistent with PFP operating
in a net glycolytic direction in the heterotrophic culture. However, the results also show that activating PFP has little
direct effect on heterotrophic carbohydrate metabolism beyond increasing the rate of cycling between hexose phosphates and
triose phosphates.
Received: 29 March 2000 / Accepted: 13 June 2000 |
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Keywords: | : Carbohydrate metabolism Fructose 2 6-bisphosphate Nicotiana (carbohydrate metabolism) Pyrophosphate: fructose-6-phosphate 1-phosphotransferase Substrate cycling Transgenic tobacco |
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