title: Genetic analysis of two Arabidopsis DNA polymerase epsilon subunits during early embryogenesis.
abstract: Accurate DNA replication is one of the most important events in the life of a cell. To perform this task, the cell utilizes several DNA polymerase complexes. We investigated the role of DNA polymerase epsilon during gametophyte and seed development using forward and reverse genetic approaches. In Arabidopsis, the catalytic subunit of this complex is encoded by two genes, AtPOL2a and AtPOL2b, whereas the second largest regulatory subunit AtDPB2 is present as a unique complete copy. Disruption of AtPOL2a or AtDPB2 resulted in a sporophytic embryo-defective phenotype, whilst mutations in AtPOL2b produced no visible effects. Loss of AtDPB2 function resulted in a severe reduction in nuclear divisions, both in the embryo and in the endosperm. Mutations in AtPOL2a allowed several rounds of mitosis to proceed, often with aberrant planes of division. Moreover, AtDPB2 was not expressed during development of the female gametophyte, which requires three post-meiotic nuclear divisions. Since a consensus binding site for E2F transcription factors was identified in the promoter region of both genes, the promoter-reporter fusion technique was used to show that luciferase activity was increased at specific phases of the cell cycle in synchronized tobacco BY-2 cells. Our results support the idea that fertilization may utilize the mechanisms of cell cycle transcriptional regulation of genes to reactivate the divisions of the oosphere and central cell.
authors.affiliation: Laboratoire Génome et Développement des Plantes, UMR-CNRS-IRD-Université 5096, 66860 Perpignan-cedex, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ronceret
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Guilleminot
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lincker
authors.forename: Jose
authors.initials: J
authors.lastname: Gadea-Vacas
authors.forename: Valérie
authors.initials: V
authors.lastname: Delorme
authors.forename: Nicole
authors.initials: N
authors.lastname: Bechtold
authors.forename: Georges
authors.initials: G
authors.lastname: Pelletier
authors.forename: Michel
authors.initials: M
authors.lastname: Delseny
authors.forename: Marie-Edith
authors.initials: ME
authors.lastname: Chabouté
authors.forename: Martine
authors.initials: M
authors.lastname: Devic
mesh_terms: D017360:Arabidopsis / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002453:Cell Cycle; D002478:Cells, Cultured; D004257:DNA Polymerase II / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D047108:Embryonic Development; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000648:ultrastructure; D014026:Nicotiana / Q000166:cytology
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C507135:DPB2 protein, Arabidopsis; D021122:Protein Subunits; C507136:POL2a protein, Arabidopsis; C507137:POL2b protein, Arabidopsis; D004257:DNA Polymerase II