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Epigenetic maintenance of the vernalized state in Arabidopsis thaliana requires LIKE HETEROCHROMATIN PROTEIN 1


Vernalization is the process by which sensing a prolonged exposure to winter cold leads to competence to flower in the spring. In winter annual Arabidopsis thaliana accessions, flowering is suppressed in the fall by expression of the potent floral repressor FLOWERING LOCUS C (FLC)1. Vernalization promotes flowering via epigenetic repression of FLC2. Repression is accompanied by a series of histone modifications of FLC chromatin that include dimethylation of histone H3 at Lys9 (H3K9) and Lys27 (H3K27)3,4. Here, we report that A. thaliana LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) is necessary to maintain the epigenetically repressed state of FLC upon return to warm conditions typical of spring. LHP1 is enriched at FLC chromatin after prolonged exposure to cold, and LHP1 activity is needed to maintain the increased levels of H3K9 dimethylation at FLC chromatin that are characteristic of the vernalized state.

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We are grateful to S. Woody, R. Schmitz and R. Rodman for their comments on the manuscript. Research in the laboratory of R.M.A. was supported by the College of Agricultural and Life Sciences of the University of Wisconsin and by grants from the US Department of Agriculture National Research Initiative Competitive Grants Program and the National Science Foundation. Research in the laboratory of S.E.J. was supported by US National Institute of Health grant GM060398.

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Competing interests

The authors declare no competing financial interests.

Correspondence to Richard M Amasino.

Supplementary information

Supplementary Fig. 1

LHP1 localization. (PDF 257 kb)

Supplementary Table 1

Primers used for ChIP and RT-PCR. (PDF 38 kb)

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Figure 1: The vernalization response is impaired in lhp1 mutants.
Figure 2: Role of LHP1 in FLC repression.
Figure 3: ChIP analyses of FLC chromatin.
Figure 4: A region in the first intron of FLC is essential for maintenance of the vernalized state.