In some plant species, prolonged exposure to low temperature during the winter season is necessary to acquire the competence to flower in the following spring. This process, known as vernalization, is an epigenetic change in which a mitotically stable change of the developmental potential of the meristem (competence to flower) is maintained even in the absence of the inducing signal (prolonged cold exposure). In Arabidopsis, vernalization results in stable epigenetic repression of a potent floral repressor, FLOWERING LOCUS C (FLC). Increased enrichment of Polycomb Repressive Complex 2 (PRC2) and trimethylated Histone H3 Lys 27 (H3K27me3) at FLC chromatin is necessary for the stable maintenance of FLC repression by vernalization. A long intronic noncoding RNA (termed as COLDAIR) is required for the vernalization-mediated epigenetic repression of FLC. COLDAIR physically associates with a component of PRC2 and targets PRC2 to FLC. COLDAIR is required for establishing stable repressive chromatin at FLC through its interaction with PRC2. In addition, floral integrator genes are targets of PRC2 complex, resulting in delayed flowering time through repression mechanism of PRC2 complex. Recently another long non-coding RNA was isolated from floral integrator gene and characterized the function of this long non coding RNA.

• Jae Bok Heo(Department of Molecular Biotechnology, Dong-A University) Corresponding Author