May be a transcription factor part of a circadian clock input pathway. Acts within a 'zeitnehmer' feedback loop and is involved in its own circadian regulation. Has no role in regulating circadian clock function in the dark. Part of a corepressor complex consisting of ELF4, ELF3, and LUX involved in the transcriptional regulation of APRR9. The activity of the protein may be decreased in long day conditions due to its interaction with phytochrome B (phyB). Can regulate the initiation of flowering independently of phyB. Also involved in responses to nematode parasitism, like the formation of the nematode feeding structure. Interacts specifically with both Pr and Pfr forms of phytochrome B. Interacts with ELF4. May form a homodimer. Forms nuclear bodies. Expressed with a circadian rhythm showing a peak 14 to 16 hours after sunrise regardless of day length. Induced in roots after infection by nematodes. Up-regulated by auxin and cytokinin and down-regulated by abscisic acid and temperature stress.