Abstract
Floral stem cell activity is terminated in flower development. The negative feedback loop of the stem cell determinant WUSCHEL (WUS) and the floral homeotic protein AGAMOUS (AG) plays a major role for the meristem determinacy control in Arabidopsis. AG is directly induced by WUS in the center of floral primordia. WUS and AG are co-expressed for about two days, and then AG represses WUS expression to terminate the stem cell activity. We recently showed that KNUCKLES (KNU), a C2H2-type zinc finger protein is a direct target of AG, mediating the repression of WUS. We show that the KNU locus contains the repressive histone mark H3Lys27 tri-methylation (H3K27me3) and that the AG-dependent removal of the mark happens in a cell-cycle dependent manner. We further show that AG binding sites contain the landing site for a Polycomb Group (PcG) protein necessary for the maintenance of H3K27me3. These results indicate that the competition of AG with the PcG leads to dilution of H3K27me3 during cell division. I will present our model that the negative feedback loop is regulated in a proper developmental timing through histone modification.
