Role of chromatin modification in flowering-time control.

The regulation of the FLC locus provides a plant model of how chromatin-modifying systems have emerged as important components in the control of a major developmental switch, the transition to flowering. Genetic and molecular studies have revealed that three systems of FLC regulation (vernalization, FRI and the autonomous pathway) all influence the state of FLC chromatin. Histone H3 trimethylation at lysine 4 and histone acetylation are associated with active FLC expression, whereas histone deacetylation and histone H3 dimethylation at lysines 9 and 27 are involved in FLC repression. These chromatin modifications provide an additional level of regulation of gene expression beyond that of the transcription factors that recruit RNA polymerase to target genes.