A methyltransferase required for proper timing of the vernalization response in arabidopsis

Prolonged exposure to winter cold enables flowering in many plant species through a process called vernalization. In Arabidopsis, vernalization results from the epigenetic silencing of the floral repressor FLOWERING LOCUS C (FLC) via a Polycomb Repressive Complex 2 (PRC2)-mediated increase in the density of the epigenetic silencingmark H3K27me3 at FLC chromatin. During cold exposure, a gene encoding a unique, cold-specific PRC2 component, VERNALIZATION INSENSITIVE 3 (VIN3), which is necessary for PRC2-mediated silencing of FLC, is induced. Here we show that SET DOMAIN GROUP 7 (SDG7) is required for proper timing of VIN3 induction and of the vernalization process. Loss of SDG7 results in a vernalization-hypersensitive phenotype, as well as more rapid cold-mediated up-regulation of VIN3. In the absence of cold, loss of SDG7 results in elevated levels of long noncoding RNAs, which are thought to participate in epigenetic repression of FLC. Furthermore, loss of SDG7 results in increased H3K27me3 deposition on FLC chromatin in the absence of cold exposure and enhanced H3K27me3 spreading during cold treatment. Thus, SDG7 is a negative regulator of vernalization, and loss of SDG7 creates a partially vernalized state without cold exposure. vernalization flowering time SET DOMAIN GROUP 7 We thank Donna Fernandez, Xuehua Zhong and members of R.M.A.'s laboratory for useful discussions, and Juan Gao for assistance with the HMTase assays. Work in R.M.A.'s laboratory was supported by the College of Agricultural and Life Sciences, Graduate School of the University of Wisconsin; the National Institutes of Health (Grant 1R01GM079525); the Great Lakes Bioenergy Research Center (US Department of Energy Office of Biological and Environmental Research Grant DE-FCO2-07ER64494) and the National Science Foundation (Grant IOS-1258126).Work inW.H.S.'s laboratory was supported in part by the French Agence Nationale de la Recherche (Grant ANR-12-BSV2-0013-02) and the European Commission (FP7-PEOPLE-2013-ITN; Grant 607880).