Transcription activator that acts as positive regulator of seedling photomorphogenesis (PubMed:17965270). Acts downstream of COP1 and play an important role in early and long-term adjustment of the shade avoidance syndrome (SAS) responses in natural environments (PubMed:21070414). Interacts with COP1, HY5 and BBX32. Interacts with FLZ1 (PubMed:24901469). Enhanced number of emerged lateral roots.