Nuclear factor Y-mediated H3K27me3 demethylation of the SOC1 locus orchestrates flowering responses of Arabidopsis.

Nuclear factor Y (NF-Y) is a conserved heterotrimeric transcription factor complex that binds to the CCAAT motifs within the promoter region of many genes. In plants, a large number of genes code for variants of each NF-YA, B or C subunit that can assemble in a combinatorial fashion. Here, we report the discovery of an Arabidopsis NF-Y complex that exerts epigenetic control over flowering time by integrating environmental and developmental signals. We show that NF-Y interacts with CONSTANS in the photoperiod pathway and DELLAs in the gibberellin pathway, to directly regulate the transcription of SOC1, a major floral pathway integrator. This NF-Y complex binds to a unique cis-element within the SOC1 promoter to modulate trimethylated H3K27 levels, partly through a H3K27 demethylase REF6. Our findings establish NF-Y complexes as critical mediators of epigenetic marks that regulate the response to environmental or intrinsic signals in plants.