Histone acetylation is modulated through the action of histone acetyltransf
erase and deacetylase, which play key roles in the regulation of eukaryotic
gene expression. We have screened the expressed sequence tag database with
the yeast histone deacetylase RPD3 sequence and identified two Arabidopsis
homologues, AtRPD3A and AtRPD3B. The deduced amino acid sequences of AtRPD
3A and AtRPD3B show high overall homology (55% identity) to each other. AtR
PD3A encodes a putative protein of 502 amino acids with 49% identity to the
yeast RPD3. AtRPD3B encodes a putative protein of 471 amino acids and shar
es 55% amino acid identity with the yeast RPD3. Northern analysis indicated
that AtRPD3A was highly expressed in the leaves, stems, flowers and young
siliques of Arabidopsis plants, whereas the AtRPD3B transcript was not dete
cted in these organs. An AtRPD3A fusion protein repressed transcription whe
n directed to a promoter driving a reporter gene, indicating a role for AtR
PD3A protein in gene repression. Arabidopsis plants were transformed with a
gene construct comprising a truncated AtRPD3A cDNA in the antisense orient
ation driven by a strong constitutive promoter, -394tCUP. Antisense express
ion of AtRPD3A resulted in decreased endogenous AtRPD3A transcript and dela
yed flowering in transgenic Arabidopsis plants, suggesting that the transit
ion from the vegetative to reproductive phase of development could be affec
ted by histone acetylation. Our study demonstrates the important role of hi
stone deacetylases in plant growth and development.