title: Robustness of central carbohydrate metabolism in developing maize kernels.
abstract: The central carbohydrate metabolism provides the precursors for the syntheses of various storage products in seeds. While the underlying biochemical map is well established, little is known about the organization and flexibility of carbohydrate metabolic fluxes in the face of changing biosynthetic demands or other perturbations. This question was addressed in developing kernels of maize (Zea mays L.), a model system for the study of starch and sugar metabolism. (13)C-labeling experiments were carried out with inbred lines, heterotic hybrids, and starch-deficient mutants that were selected to cover a wide range of performances and kernel phenotypes. In total, 46 labeling experiments were carried out using either [U-(13)C(6)]glucose or [U-(13)C(12)]sucrose and up to three stages of kernel development. Carbohydrate flux distributions were estimated based on glucose isotopologue abundances, which were determined in hydrolysates of starch by using quantitative (13)C-NMR and GC-MS. Similar labeling patterns in all samples indicated robustness of carbohydrate fluxes in maize endosperm, and fluxes were rather stable in response to glucose or sucrose feeding and during development. A lack of ADP-glucose pyrophosphorylase in the bt2 and sh2 mutants triggered significantly increased hexose cycling. In contrast, other mutations with similar kernel phenotypes had no effect. Thus, the distribution of carbohydrate fluxes is stable and not determined by sink strength in maize kernels.
authors.affiliation: Lehrstuhl für Genetik, Technische Universität München, Am Hochanger 8, 85350 Freising, Germany.
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: Werner
authors.initials: W
authors.lastname: Römisch
authors.forename: Christian
authors.initials: C
authors.lastname: Ettenhuber
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.forename: Alfons
authors.initials: A
authors.lastname: Gierl
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisenreich
authors.forename: Ulrich
authors.initials: U
authors.lastname: Genschel
mesh_terms: D050260:Carbohydrate Metabolism; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D003313:Zea mays / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*