A metabolic flux analysis to study the role of sucrose synthase in the regulation of the carbon partitioning in central metabolism in maize root tips |
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Authors: | Alonso Ana Paula Raymond Philippe Hernould Michel Rondeau-Mouro Corinne de Graaf Albert Chourey Prem Lahaye Marc Shachar-Hill Yair Rolin Dominique Dieuaide-Noubhani Martine |
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Institution: | INRA, Université Bordeaux 1, Université Victor Segalen Bordeaux 2, UMR 619 Biologie du fruit, BP 81, 33883 Villenave d'Ornon cedex, France. |
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Abstract: | In order to understand the role of sucrose synthase (SuSy) in carbon partitioning, metabolic fluxes were analyzed in maize root tips of a double mutant of SuSy genes, sh1 sus1 and the corresponding wild type, W22. U-14C]-glucose pulse labeling experiments permitted the quantification of unidirectional fluxes into sucrose, starch and cell wall polysaccharides. Isotopic steady-state labeling with 1-13C]-, 2-13C]- or U-13C]-glucose followed by the quantification by 1H-NMR and 13C-NMR of enrichments in carbohydrates and amino acids was also performed to determine 29 fluxes through central metabolism using computer-aided modeling. As a consequence of the suppression of SUS1 and SH1 isozymes, maize root tips diameter was significantly decreased and respiratory metabolism reduced by 30%. Our result clearly established that, in maize root tips, starch is produced from ADP-Glc synthesized in the plastid and not in the cytosol by sucrose synthase. Unexpectedly, the flux of cell wall synthesis was increased in the double mutant. This observation indicates that, in maize root tips, SH1 and SUS1 are not specific providers for cellulose biosynthesis. |
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Keywords: | Sucrose synthase Metabolic flux analysis Cell wall Maize root Isotopic labeling NMR |
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