title: Changes in flux pattern of the central carbohydrate metabolism during kernel development in maize.
abstract: Developing kernels of the inbred maize line W22 were grown in sterile culture and supplied with a mixture of [U-13C6]glucose and unlabeled glucose during three consecutive intervals (11-18, 18-25, or 25-32 days after pollination) within the linear phase of starch formation. At the end of each labeling period, glucose was prepared from starch and analyzed by 13C isotope ratio mass spectrometry and high-resolution (13)C NMR spectroscopy. The abundances of individual glucose isotopologs were calculated by computational deconvolution of the NMR data. [1,2-(13)C2]-, [5,6-(13)C2]-, [2,3-(13)C2]-, [4,5-(13)C2]-, [1,2,3-(13)C3]-, [4,5,6-(13)C3]-, [3,4,5,6-(13)C4]-, and [U-(13)C6]-isotopologs were detected as the major multiple-labeled glucose species, albeit at different normalized abundances in the three intervals. Relative flux contributions by five different pathways in the primary carbohydrate metabolism were determined by computational simulation of the isotopolog space of glucose. The relative fractions of some of these processes in the overall glucose cycling changed significantly during maize kernel development. The simulation showed that cycling via the non-oxidative pentose phosphate pathway was lowest during the middle interval of the experiment. The observed flux pattern could by explained by a low demand for amino acid precursors recruited from the pentose phosphate pathway during the middle interval of kernel development.
authors.affiliation: Lehrstuhl für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ettenhuber
authors.forename: Gertraud
authors.initials: G
authors.lastname: Spielbauer
authors.forename: Lilla
authors.initials: L
authors.lastname: Margl
authors.forename: L Curtis
authors.initials: LC
authors.lastname: Hannah
authors.forename: Alfons
authors.initials: A
authors.lastname: Gierl
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.forename: Ulrich
authors.initials: U
authors.lastname: Genschel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisenreich
mesh_terms: D050260:Carbohydrate Metabolism; D019295:Computational Biology; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D003313:Zea mays / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*