Silencing by plant Polycomb-group genes requires dispersed trimethylation of histone H3 at lysine 27.
The plant Polycomb-group (Pc-G) protein CURLY LEAF (CLF) is required to repress targets such as AGAMOUS (AG) and SHOOTMERISTEMLESS (STM). Using chromatin immunoprecipitation, we identify AG and STM as direct targets for CLF and show that they carry a characteristic epigenetic signature of dispersed histone H3 lysine 27 trimethylation (H3K27me3) and localised H3K27me2 methylation. H3K27 methylation is present throughout leaf development and consistent with this, CLF is required persistently to silence AG. However, CLF is not itself an epigenetic mark as it is lost during mitosis. We suggest a model in which Pc-G proteins are recruited to localised regions of targets and then mediate dispersed H3K27me3. Analysis of transgenes carrying AG regulatory sequences confirms that H3K27me3 can spread to novel sequences in a CLF-dependent manner and further shows that H3K27me3 methylation is not sufficient for silencing of targets. We suggest that the spread of H3K27me3 contributes to the mitotic heritability of Pc-G silencing, and that the loss of silencing caused by transposon insertions at plant Pc-G targets reflects impaired spreading.
Schubert
Daniel
D
Institute for Molecular Plant Sciences, School of Biology, University of Edinburgh, Edinburgh, UK.
Primavesi
Lucia
L
Bishopp
Anthony
A
Roberts
Gethin
G
Doonan
John
J
Jenuwein
Thomas
T
Goodrich
Justin
J
D026342:AGAMOUS Protein, Arabidopsis / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003080:Cold Temperature; D004268:DNA-Binding Proteins; D020868:Gene Silencing; D017343:Genes, Plant / Q000235:genetics*; D006657:Histones / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D026161:MADS Domain Proteins / Q000378:metabolism; D008745:Methylation; D008938:Mitosis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology; D018517:Plant Roots / Q000166:cytology; D017354:Point Mutation / Q000235:genetics; D063146:Polycomb-Group Proteins; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics*; D019076:Transgenes
D026342:AGAMOUS Protein, Arabidopsis; D029681:Arabidopsis Proteins; C104597:CURLY LEAF protein, Arabidopsis; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C418902:At5g10140 protein, Arabidopsis; D006657:Histones; D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D009687:Nuclear Proteins; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins; C097496:STM protein, Arabidopsis; C442836:VRN2 protein, Arabidopsis; D008239:Lysine