title: Polycomb group complexes self-regulate imprinting of the Polycomb group gene MEDEA in Arabidopsis.
abstract: Fertilization in flowering plants initiates the development of the embryo and endosperm, which nurtures the embryo. A few genes subjected to imprinting are expressed in endosperm from their maternal allele, while their paternal allele remains silenced. Imprinting of the FWA gene involves DNA methylation. Mechanisms controlling imprinting of the Polycomb group (Pc-G) gene MEDEA (MEA) are not yet fully understood. Here we report that MEA imprinting is regulated by histone methylation. This epigenetic chromatin modification is mediated by several Pc-G activities during the entire plant life cycle. We show that Pc-G complexes maintain MEA transcription silenced throughout vegetative life and male gametogenesis. In endosperm, the maternal allele of MEA encodes an essential component of a Pc-G complex, which maintains silencing of the paternal MEA allele. Hence, we conclude that a feedback loop controls MEA imprinting. This feedback loop ensures a complete maternal control of MEA expression from both parental alleles and might have provided a template for evolution of imprinting in plants.
authors.affiliation: Chromatin and Reproduction Group, Temasek LifeSciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Republic of Singapore.
authors.forename: Pauline E
authors.initials: PE
authors.lastname: Jullien
authors.forename: Aviva
authors.initials: A
authors.lastname: Katz
authors.forename: Moran
authors.initials: M
authors.lastname: Oliva
authors.forename: Nir
authors.initials: N
authors.lastname: Ohad
authors.forename: Frédéric
authors.initials: F
authors.lastname: Berger
mesh_terms: D017360:Arabidopsis / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly; D047369:Chromatin Immunoprecipitation; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D018392:Genomic Imprinting; D006657:Histones / Q000378:metabolism; D008745:Methylation; D008957:Models, Genetic; D063146:Polycomb-Group Proteins; D011499:Protein Processing, Post-Translational; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology*; D012639:Seeds / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D006657:Histones; C111712:MEA protein, Arabidopsis; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins