Vernalization requires epigenetic silencing of FLC by histone methylation.
To ensure flowering in favourable conditions, many plants flower only after an extended period of cold, namely winter. In Arabidopsis, the acceleration of flowering by prolonged cold, a process called vernalization, involves downregulation of the protein FLC, which would otherwise prevent flowering. This lowered FLC expression is maintained through subsequent development by the activity of VERNALIZATION (VRN) genes. VRN1 encodes a DNA-binding protein whereas VRN2 encodes a homologue of one of the Polycomb group proteins, which maintain the silencing of genes during animal development. Here we show that vernalization causes changes in histone methylation in discrete domains within the FLC locus, increasing dimethylation of lysines 9 and 27 on histone H3. Such modifications identify silenced chromatin states in Drosophila and human cells. Dimethylation of H3 K27 was lost only in vrn2 mutants, but dimethylation of H3 K9 was absent from both vrn1 and vrn2, consistent with VRN1 functioning downstream of VRN2. The epigenetic memory of winter is thus mediated by a 'histone code' that specifies a silent chromatin state conserved between animals and plants.
Bastow
Ruth
R
Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK.
Mylne
Joshua S
JS
Lister
Clare
C
Lippman
Zachary
Z
Martienssen
Robert A
RA
Dean
Caroline
C
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly; D003080:Cold Temperature; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant / Q000235:genetics; D006657:Histones / Q000378:metabolism*; D026161:MADS Domain Proteins / Q000235:genetics*; D008745:Methylation; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D012621:Seasons; D016335:Zinc Fingers
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; C418902:At5g10140 protein, Arabidopsis; D006657:Histones; D026161:MADS Domain Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C461388:VRN1 protein, Arabidopsis; C442836:VRN2 protein, Arabidopsis