MSI4/FVE interacts with CUL4–DDB1 and a PRC2-like complex to control epigenetic regulation of flowering time in Arabidopsis

Flowering at the right time is crucial to ensure successful plant reproduction and seed yield and is dependent on both environmental and endogenous parameters. Among the different pathways that impinge on flowering, the autonomous pathway promotes floral transition independently of day length through the repression of the central flowering repressorFLOWERING LOCUS C (FLC ). FLC blocks floral transition by repressing flowering time integrators such asFLOWERING LOCUS T (FT ). MSI4/FVE is a key regulator of the autonomous pathway that reducesFLC expression. Here we report that the MSI4 protein is a DDB1 and CUL4-associated factor that repressesFLC expression through its association with a CLF-Polycomb Repressive Complex 2 (PRC2) inArabidopsis . Thus, the lack of MSI4 or decreased CUL4 activity reduces H3K27 trimethylation onFLC, but also on its downstream targetFT, resulting in increased expression of both genes. Moreover, CUL4 interacts withFLC chromatin in an MSI4-dependant manner, and the interaction between MSI4 and CUL4–DDB1 is necessary for the epigenetic repression ofFLC . Overall our work provides evidence for a unique functional interaction between the cullin-RING ubiquitin ligase (CUL4–DDB1MSI4 ) and a CLF–PRC2 complex in the regulation of flowering timing inArabidopsis .