Some genetic studies indicate that plant homologues of proteins involved in 
chromatin modification and remodeling in other organisms may regulate plant 
development. Previously, we described an Arabidopsis mutant with altered 
cold-responsive gene expression (acg1) displaying a late flowering phenotype, a 
null allele of fve. FVE is a homologue of the mammalian 
retinoblastoma-associated protein (RbAp), one component of a histone deacetylase 
(HDAC) complex involved in transcriptional repression, and has been shown to be 
involved in the deacetylation of the FLOWERING LOCUS C (FLC) chromatin encoding 
for a repressor of flowering. In an effort to gain insight into the biochemical 
functions of FVE, we overexpressed FVE tagged with the hemagglutinin (HA) and 
FLAG epitope at the N-terminus in acg1 mutants. The results of physiological and 
molecular analyses demonstrated that FVE overexpression in acg1 rescued the 
mutant phenotypes, including late flowering and alterations in floral pathway 
gene expression such as FLC, SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), and 
FLOWERING LOCUS T (FT), and also super-induced cold-responsive reporter gene 
expression. The chromatin immunoprecipitation experiments revealed the 
amplification of specific DNA regions of FLC and COLD-REGULATED 15A (COR15A), 
indicating that FVE may bind to the FLC and COR15A chromatin. Gel-filtration 
chromatography and the immunoprecipitation of putative FVE complexes showed that 
FVE forms a protein complex of approximately 1.0 MDa. These results demonstrate 
that FVE may exist as a multiprotein complex, similar to the mammalian HDAC 
complex harboring RbAp, to regulate flowering time and cold response by 
associating with the FLC and COR chromatin.