title: Early carbon mobilization and radicle protrusion in maize germination.
abstract: Considerable amounts of information is available on the complex carbohydrates that are mobilized and utilized by the seed to support early seedling development. These events occur after radicle has protruded from the seed. However, scarce information is available on the role of the endogenous soluble carbohydrates from the embryo in the first hours of germination. The present work analysed how the soluble carbohydrate reserves in isolated maize embryos are mobilized during 6-24 h of water imbibition, an interval that exclusively embraces the first two phases of the germination process. It was found that sucrose constitutes a very significant reserve in the scutellum and that it is efficiently consumed during the time in which the adjacent embryo axis is engaged in an active metabolism. Sucrose transporter was immunolocalized in the scutellum and in vascular elements. In parallel, a cell-wall invertase activity, which hydrolyses sucrose, developed in the embryo axis, which favoured higher glucose uptake. Sucrose and hexose transporters were active in the embryo tissues, together with the plasma membrane H(+)-ATPase, which was localized in all embryo regions involved in both nutrient transport and active cell elongation to support radicle extension. It is proposed that, during the initial maize germination phases, a net flow of sucrose takes place from the scutellum towards the embryo axis and regions that undergo elongation. During radicle extension, sucrose and hexose transporters, as well as H(+)-ATPase, become the fundamental proteins that orchestrate the transport of nutrients required for successful germination.
authors.affiliation: Departamento de Bioquímica, Facultad de Química, Conjunto E. Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, 04510, DF, México.
authors.forename: Luis
authors.initials: L
authors.lastname: Sánchez-Linares
authors.forename: Marina
authors.initials: M
authors.lastname: Gavilanes-Ruíz
authors.forename: David
authors.initials: D
authors.lastname: Díaz-Pontones
authors.forename: Fernando
authors.initials: F
authors.lastname: Guzmán-Chávez
authors.forename: Viridiana
authors.initials: V
authors.lastname: Calzada-Alejo
authors.forename: Viridiana
authors.initials: V
authors.lastname: Zurita-Villegas
authors.forename: Viridiana
authors.initials: V
authors.lastname: Luna-Loaiza
authors.forename: Rafael
authors.initials: R
authors.lastname: Moreno-Sánchez
authors.forename: Irma
authors.initials: I
authors.lastname: Bernal-Lugo
authors.forename: Sobeida
authors.initials: S
authors.lastname: Sánchez-Nieto
mesh_terms: D000818:Animals; D001692:Biological Transport; D050260:Carbohydrate Metabolism / Q000502:physiology*; D049108:Cell Enlargement; D005632:Fructose / Q000032:analysis / Q000378:metabolism; D018525:Germination / Q000502:physiology*; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010101:Oxygen Consumption; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011817:Rabbits; D036226:Seedlings / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000201:enzymology / Q000254:growth & development / Q000502:physiology*; D013395:Sucrose / Q000032:analysis / Q000378:metabolism; D014280:Triglycerides / Q000032:analysis / Q000378:metabolism; D014867:Water / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology / Q000254:growth & development / Q000276:immunology / Q000502:physiology*; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins; D014280:Triglycerides; D014867:Water; D005632:Fructose; D013395:Sucrose; D043324:beta-Fructofuranosidase; D006180:Proton-Translocating ATPases; D005947:Glucose