Regulation of Flowering Time by Histone Acetylation in Arabidopsis

The Arabidopsis autonomous floral-promotion pathway promotes flowering independently of the photoperiod and vernalization pathways by repressing FLOWERING LOCUS C ( FLC ), a MADS-boxtranscription factor that blocks the transition from vegetative to reproductive development. Here, we report that FLOWERING LOCUS D ( FLD ), one of sixgenes in the autonomous pathway, encodes a plant homolog of a protein found in histone deacetylase complexes in mammals. Lesions in FLD result in hyperacetylation of histones in FLC chromatin, up-regulation of FLC expression, and extremely delayed flowering. Thus, the autonomous pathway regulates flowering in part by histone deacetylation. However, not all autonomous-pathway mutants exhibit FLC hyperacetylation, indicating that multiple means exist by which this pathway represses FLC expression.