Journal Article

Modulation of Fructokinase Activity of Potato (<i>Solanum tuberosum</i>) Results in Substantial Shifts in Tuber Metabolism

Howard V. Davies, Louise V. T. Shepherd, Michael M. Burrell, Fernando Carrari, Ewa Urbanczyk-Wochniak, Andrea Leisse, Robert D. Hancock, Mark Taylor, Roberto Viola, Heather Ross, Diane McRae, Lothar Willmitzer and Alisdair R. Fernie

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 7, pages 1103-1115
Published in print July 2005 | ISSN: 0032-0781
Published online July 2005 | e-ISSN: 1471-9053 | DOI:
Modulation of Fructokinase Activity of Potato (Solanum tuberosum) Results in Substantial Shifts in Tuber Metabolism

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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Potato plants (Solanum tuberosum L. cvs Desiree and Record) transformed with sense and antisense constructs of a cDNA encoding the potato fructokinase StFK1 exhibited altered transcription of this gene, altered amount of protein and altered enzyme activities. Measurement of the maximal catalytic activity of fructokinase revealed a 2-fold variation in leaf (from 90 to 180% of wild type activity) and either a 10- or 30-fold variation in tuber (from 10 or 30% to 300% in Record and Desiree, respectively) activity. The comparative effect of the antisense construct in leaf and tuber tissue suggests that this isoform is only a minor contributor to the total fructokinase activity in the leaf but the predominant isoform in the tuber. Antisense inhibition of the fructokinase resulted in a reduced tuber yield; however, its overexpression had no impact on this parameter. The modulation of fructokinase activity had few, consistent effects on carbohydrate levels, with the exception of a general increase in glucose content in the antisense lines, suggesting that this enzyme is not important for the control of starch synthesis. However, when metabolic fluxes were estimated, it became apparent that the transgenic lines display a marked shift in metabolism, with the rate of redistribution of radiolabel to sucrose markedly affected by the activity of fructokinase. These data suggest an important role for fructokinase, acting in concert with sucrose synthase, in maintaining a balance between sucrose synthesis and degradation by a mechanism independent of that controlled by the hexose phosphate-mediated activation of sucrose phosphate synthase.

Keywords: Carbohydrate metabolism; Fructokinase; Glycolysis; Solanum tuberosum; Starch synthesis; AGPase, ADPglucose pyrophosphorylase; CaMV, cauliflower mosaic virus; FK, fructokinase; GC-MS, gas chromatography–mass spectrometry; PBS, phosphate-buffered saline

Journal Article.  9894 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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