Journal Article

Expression of a Bacterial Xylose Isomerase in Potato Tubers Results in an Altered Hexose Composition and a Consequent Induction of Metabolism

Ewa Urbanczyk-Wochniak, Andrea Leisse, Ute Roessner-Tunali, Anna Lytovchenko, Jörg Reismeier, Lothar Willmitzer and Alisdair R. Fernie

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 12, pages 1359-1367
Published in print December 2003 | ISSN: 0032-0781
Published online December 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg166
Expression of a Bacterial Xylose Isomerase in Potato Tubers Results in an Altered Hexose Composition and a Consequent Induction of Metabolism

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  • Biochemistry
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Here we investigate the role of hexoses in the metabolism of the developing potato (Solanum tuberosum) tuber by the expression of a bacterial xylose isomerase which catalyzes the interconversion of glucose and fructose. Previously, we found that glycolysis was induced in transgenic tubers expressing a yeast invertase in the cytosol and postulated that this was due either to the decreased levels of sucrose or to effects downstream of the sucrose cleavage. In the present study xylose isomerase was expressed under the control of the tuber-specific patatin promoter. Selected transformants exhibited minor changes in the levels of tuber glucose and fructose but not in sucrose. Analysis of the enzyme activities of the glycolytic pathway revealed minor yet significant increases in the maximal catalytic activities of aldolase and glyceraldehyde 3-phosphate dehydrogenase but no increase in the activities of other enzymes of glycolysis. These lines were also characterized by an elevated tuber number, glycolytic and sucrose synthetic fluxes and in some metabolite levels downstream of glycolysis. When considered together these data suggest that the perturbation of hexose levels can result in increased glycolytic and sucrose (re)synthetic fluxes in the potato tuber even in the absence of changes in the level of sucrose. The consequences of altering hexose levels in the tuber are, however, not as severe as those observed following perturbation of the level of tuber sucrose.

Keywords: Keywords: Fructose — Glucose — Glycolysis — Invertase — Potato (Solanum tuberosum) tuber — Xylose isomerase.; Abbreviations: 3-PGA, 3-phosphoglycerate; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; TPI, triose phosphate isomerase; SPS, sucrose phosphate synthase.

Journal Article.  7232 words.  Illustrated.

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

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