title: Arabidopsis haiku mutants reveal new controls of seed size by endosperm.
abstract: In flowering plants, maternal seed integument encloses the embryo and the endosperm, which are both derived from double fertilization. Although the development of these three components must be coordinated, we have limited knowledge of mechanisms involved in such coordination. The endosperm may play a central role in these mechanisms as epigenetic modifications of endosperm development, via imbalance of dosage between maternal and paternal genomes, affecting both the embryo and the integument. To identify targets of such epigenetic controls, we designed a genetic screen in Arabidopsis for mutants that phenocopy the effects of dosage imbalance in the endosperm. The two mutants haiku 1 and haiku 2 produce seed of reduced size that resemble seed with maternal excess in the maternal/paternal dosage. Homozygous haiku seed develop into plants indistinguishable from wild type. Each mutation is sporophytic recessive, and double-mutant analysis suggests that both mutations affect the same genetic pathway. The endosperm of haiku mutants shows a premature arrest of increase in size that causes precocious cellularization of the syncytial endosperm. Reduction of seed size in haiku results from coordinated reduction of endosperm size, embryo proliferation, and cell elongation of the maternally derived integument. We present further evidence for a control of integument development mediated by endosperm-derived signals.
authors.affiliation: European Molecular Biology Organization (EMBO) YIP team, Ecole Normal Supérieure de Lyon, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Lyon I, 46 Allée d'Italie, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Garcia
authors.forename: Virginie
authors.initials: V
authors.lastname: Saingery
authors.forename: Pierre
authors.initials: P
authors.lastname: Chambrier
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mayer
authors.forename: Gerd
authors.initials: G
authors.lastname: Jürgens
authors.forename: Frédéric
authors.initials: F
authors.lastname: Berger
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D012639:Seeds / Q000166:cytology / Q000235:genetics* / Q000254:growth & development* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins