Probable transcription factor that acts as a positive regulator of continuous red light signals downstream of phytochrome B (phyB). Required for the regulation of hypocotyl elongation during de-etiolation. May be required to modulate phytochrome A (phyA) signal transduction in a phyB-independent way. Mainly cytoplasmic. Expressed in roots, hypocotyls, cotyledons, shoot apex, leaves, flowers and siliques. During development, higher expression levels are detected in young rosette leaves, senescing leaves and petals and sepals at flower stage 15. By osmotic and cold stresses, and UV-A/B. Belongs to the GRAS family. Extended C-terminus.