title: Identification of new members of Fertilisation Independent Seed Polycomb Group pathway involved in the control of seed development in Arabidopsis thaliana.
abstract: In higher plants, double fertilisation initiates seed development. One sperm cell fuses with the egg cell and gives rise to the embryo, the second sperm cell fuses with the central cell and gives rise to the endosperm. The endosperm develops as a syncytium with the gradual organisation of domains along an anteroposterior axis defined by the position of the embryo at the anterior pole and by the attachment to the placenta at the posterior pole. We report that ontogenesis of the posterior pole in Arabidopsis thaliana involves oriented migration of nuclei in the syncytium. We show that this migration is impaired in mutants of the three founding members of the FERTILIZATION INDEPENDENT SEED (FIS) class, MEDEA (MEA), FIS2 and FERTILIZATION INDEPENDENT ENDOSPERM (FIE). A screen based on a green fluorescent protein (GFP) reporter line allowed us to identify two new loci in the FIS pathway, medicis and borgia. We have cloned the MEDICIS gene and show that it encodes the Arabidopsis homologue of the yeast WD40 domain protein MULTICOPY SUPRESSOR OF IRA (MSI1). The mutations at the new fis loci cause the same cellular defects in endosperm development as other fis mutations, including parthenogenetic development, absence of cellularisation, ectopic development of posterior structures and overexpression of the GFP marker.
authors.affiliation: EMBO YIP Team, Unité Mixte de Recherche 5667, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, F-69364 Lyon cedex 07, France.
authors.forename: Anne-Elisabeth
authors.initials: AE
authors.lastname: Guitton
authors.forename: Damian R
authors.initials: DR
authors.lastname: Page
authors.forename: Pierre
authors.initials: P
authors.lastname: Chambrier
authors.forename: Claire
authors.initials: C
authors.lastname: Lionnet
authors.forename: Jean-Emmanuel
authors.initials: JE
authors.lastname: Faure
authors.forename: Ueli
authors.initials: U
authors.lastname: Grossniklaus
authors.forename: Frédéric
authors.initials: F
authors.lastname: Berger
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics*; D016764:Cell Polarity / Q000235:genetics; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D005306:Fertilization / Q000235:genetics; D005720:Gamma Rays; D012097:Repressor Proteins / Q000032:analysis / Q000235:genetics*; D012639:Seeds / Q000502:physiology* / Q000528:radiation effects; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; C118816:FIE protein, Arabidopsis; C117389:FIS2 protein, Arabidopsis; C111712:MEA protein, Arabidopsis; D012097:Repressor Proteins; D014157:Transcription Factors