title: Arabidopsis MSI1 is a component of the MEA/FIE Polycomb group complex and required for seed development.
abstract: Seed development in angiosperms initiates after double fertilization, leading to the formation of a diploid embryo and a triploid endosperm. The active repression of precocious initiation of certain aspects of seed development in the absence of fertilization requires the Polycomb group proteins MEDEA (MEA), FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) and FERTILIZATION-INDEPENDENT SEED2. Here we show that the Arabidopsis WD-40 domain protein MSI1 is present together with MEA and FIE in a 600 kDa complex and interacts directly with FIE. Mutant plants heterozygous for msi1 show a seed abortion ratio of 50% with seeds aborting when the mutant allele is maternally inherited, irrespective of a paternal wild-type or mutant MSI1 allele. Further more, msi1 mutant gametophytes initiate endosperm development in the absence of fertilization at a high penetrance. After pollination, only the egg cell becomes fertilized, the central cell starts dividing prior to fertilization, resulting in the formation of seeds containing embryos surrounded by diploid endosperm. Our results establish that MSI1 has an essential function in the correct initiation and progression of seed development.
authors.affiliation: Institute of Plant Biology and Zurich-Basel Plant Science Centre, University of Zurich, Zollikerstrasse 107, CH-8050 Zurich, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Köhler
authors.forename: Lars
authors.initials: L
authors.lastname: Hennig
authors.forename: Romaric
authors.initials: R
authors.lastname: Bouveret
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Gheyselinck
authors.forename: Ueli
authors.initials: U
authors.lastname: Grossniklaus
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Gruissem
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D002850:Chromatography, Gel; D003433:Crosses, Genetic; D017931:DNA Primers; D005816:Genetic Complementation Test; D006579:Heterozygote; D016254:Mutagenesis, Insertional; D011003:Ploidies; D063146:Polycomb-Group Proteins; D016133:Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D012098:Reproduction; D012639:Seeds / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C475821:MSI1 protein, Arabidopsis; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins