Polycomb proteins regulate the quantitative induction of VERNALIZATION INSENSITIVE 3 in response to low temperatures.
Vernalization, the promotion of flowering in response to low temperatures, is one of the best characterized examples of epigenetic regulation in plants. The promotion of flowering is proportional to the duration of the cold period, but the mechanism by which plants measure time at low temperatures has been a long-standing mystery. We show that the quantitative induction of the first gene in the Arabidopsis vernalization pathway, VERNALIZATION INSENSITIVE 3 (VIN3), is regulated by the components of Polycomb Response Complex 2, which trimethylates histone H3 lysine 27 (H3K27me3). In differentiated animal cells, H3K27me3 is mostly associated with long-term gene repression, whereas, in pluripotent embyonic stem cells, many cell lineage-specific genes are inactive but exist in bivalent chromatin that carries both active (H3K4me3) and repressive (H3K27me3) marks on the same molecule. During differentiation, bivalent domains are generally resolved to an active or silent state. We found that H3K27me3 maintains VIN3 in a repressed state prior to cold exposure; this mark is not removed during VIN3 induction. Instead, active VIN3 is associated with bivalently marked chromatin. The continued presence of H3K27me3 ensures that induction of VIN3 is proportional to the duration of the cold, and that plants require prolonged cold to promote the transition to flowering. The observation that Polycomb proteins control VIN3 activity defines a new role for Polycomb proteins in regulating the rate of gene induction.
CSIRO, Climate Adaptation Flagship, Canberra, ACT 2601, Australia. jean.finnegan@csiro.au
E
E
Jean Finnegan
Donna M
DM
Bond
Diana M
DM
Buzas
Justin
J
Goodrich
Christopher A
CA
Helliwell
Yosuke
Y
Tamada
Jae-Young
JY
Yun
Richard M
RM
Amasino
Elizabeth S
ES
Dennis
D000107:Acetylation; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D003080:Cold Temperature; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D044127:Epigenesis, Genetic; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D051548:Histone Acetyltransferases / Q000378:metabolism; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D006657:Histones / Q000378:metabolism; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D009154:Mutation; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D063146:Polycomb-Group Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D013312:Stress, Physiological; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015854:Up-Regulation / Q000235:genetics
D029681:Arabidopsis Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D051548:Histone Acetyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones; D026161:MADS Domain Proteins; D063146:Polycomb-Group Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C418902:At5g10140 protein, Arabidopsis; C477788:At5g17690 protein, Arabidopsis; C480553:VIN3 protein, Arabidopsis; C571004:VIP4 protein, Arabidopsis; C556085:LAZ2 protein, Arabidopsis