Developmental regulator acting by forming heterodimeric complexes, that sequester CO and CO-like (COL) proteins into non-functional complexes (PubMed:27015278). Involved in the CO-mediated long-day flowering-promotion pathway (PubMed:27015278). Engages CO and the transcriptional repressor TPL in a tripartite complex (By similarity). Involved in the CO-mediated long-day flowering-promotion pathway (PubMed:27015278). Highly expressed in shoot apical meristems and in vascular tissues of leaves. Also detected in petioles. Circadian-regulation. Peak of expression toward the end of the dark period in both long day and short day photoperiods.