title: Spatial analysis of plant metabolism: sucrose imaging within Vicia faba cotyledons reveals specific developmental patterns.
abstract: During legume embryogenesis the differentiation of the cotyledons proceeds gradually in a wave-like manner. The process is metabolically and genetically controlled and regulated by sugars. In order to perform a spatial and temporal analysis of the sugar distribution pattern a new method was developed to specifically measure sucrose directly in tissues via bioluminescence and single photon counting. This enabled a quantitative sucrose imaging with a resolution close to the single cell level. The procedure was applied on sections of Vicia faba cotyledons covering the main stages of histodifferentiation. Young embryos before the storage phase contained moderate levels of sucrose, which were evenly distributed. At the onset of maturation high concentrations were present within a tissue layer covering the outward half of the coytledons. This layer was directly underneath the epidermis expressing a sucrose transporter gene indicating that epidermal transporters caused the high sucrose accumulation in the underlying tissue. At that stage the sucrose gradient was inversely oriented compared with cell size and the starch content. Cells within the interior were larger, contained starch but low sucrose. Thus, the sucrose pattern is controlled by uptake activity and permeability within the parenchyma. However, during the main storage phase actively elongating and starch accumulating cells contain highest sucrose concentrations indicating that differences in growth and starch accumulation also affect intracotyledonary sugar distribution. High sucrose concentrations were correlated with transcript levels of sucrose synthase and ADP-Glc pyrophosphorylase indicating a signaling function for sucrose to induce starch biosynthesis on the gene expression level. Carbon flux through the sucrose synthase pathway towards starch increased when hexoses levels decreased.
authors.affiliation: Institut für Pflanzengenetik und Kulturpflanzenforschung , D-06466 Gatersleben, Germany.
authors.forename: Ljudmilla
authors.initials: L
authors.lastname: Borisjuk
authors.forename: Stefan
authors.initials: S
authors.lastname: Walenta
authors.forename: Hardy
authors.initials: H
authors.lastname: Rolletschek
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Mueller-Klieser
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wobus
authors.forename: Hans
authors.initials: H
authors.lastname: Weber
mesh_terms: D050260:Carbohydrate Metabolism; D002454:Cell Differentiation; D048429:Cell Size; D007887:Fabaceae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D051599:Glucose-1-Phosphate Adenylyltransferase; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D008027:Light; D008163:Luminescent Measurements; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; C078729:sucrose transport protein, plant; D013395:Sucrose; D013213:Starch; D005964:Glucosyltransferases; C022699:sucrose synthase; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase