COP1 and BBXs‐HY5‐mediated light signal transduction in plants

Summary Light is one of the most essential environmental factors affecting many aspects of growth and developmental processes in plants. Plants undergo skotomorphogenic or photomorphogenic development dependent on the absence or presence of light. These two developmental programs enable a germinated seed to become a healthy seedling at the early stage of the plant life cycle. CULLIN 4‐DNA DAMAGE‐BINDING PROTEIN 1 (DDB1)‐based CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1)‐SUPPRESSOR OF PHYA and COP10‐DEETIOLATED 1‐DDB1 E3 ubiquitin ligase complexes promote the skotomorphogenesis by ubiquitinating and degrading a number of photomorphogenic‐promoting factors in darkness. Photoreceptors sense and transduce light information to downstream signaling, thereby initiating a set of molecular events and subsequent photomorphogenesis. These processes are precisely modulated by a group of components including various photoreceptors, E3 ubiquitin ligase, and transcription factors at the molecular level. This review provides an overview of the current understanding of the COP1, ELONGATED HYPOCOTYL 5, and B‐BOX CONTAINING PROTEINs‐mediated light signal transduction pathway and highlights still open questions in the field.