Carbon metabolism in leaves of transgenic tobacco (Nicotiana tabacum L.) containing elevated fructose 2,6-bisphosphate levels |
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Authors: | Peter Scott Alex J Lange Simon J Pilkis Nicholas J Kruger |
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Institution: | Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK; Department of Biochemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA |
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Abstract: | The aim of this work was to investigate the role of fructose 2,6-bisphosphate (Fru 2,6-P2) during photosynthesis. The level of Fru 2,6-P2 in tobacco plants was elevated by the introduction of a modified mammalian gene encoding 6-phosphofructo-2-kinase (6-PF-2-K). Estimates of the metabolite control coefficient (C) for Fru 2,6-P2 levels in response to increased 6-PF-2-K activity, suggest that small increases in 6-PF-2-K activity have little effect upon steady-state Fru 2,6-P2 levels (C = +0.08 for a 0–58% increase in 6-PF-2-K activity). However, larger changes resulted in dramatic rises in Fru 2,6-P2 levels (C = +3.35 for 206–268% increase in 6-PF-2-K activity). Transgenic plants contained Fru 2,6-P2 levels in the dark that ranged from 104 to 230% of the level in wild-type tobacco. Plants with altered levels of Fru 2,6-P2 were used to determine the effects of this signal metabolite upon carbohydrate metabolism during the initial phase of the light period. Here we provide direct evidence that Fru 2,6-P2 contributes to the regulation of carbon partitioning in tobacco leaves by inhibiting sucrose synthesis. |
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