Beyond repression of photomorphogenesis: role switching of COP/DET/FUS in light signaling

•Functional diversity of COP/DET/FUS proteins has been revealed.•COP1 promotes UV-B-induced photomorphogenesis.•The regulation of COP1 by blue and UV-B light has been biochemically defined.•The organization of COP/DET/FUS complexes is directed by light signals.

Light is a pivotal environmental stimulus that promotes plant photomorphogenesis. Substantial progress has been achieved in defining the central repressors of photomorphogenesis, the CONSTITUTIVE PHOTOMORPHOGENIC/DE-ETIOLATED/FUSCA (COP/DET/FUS) loci, in the past 20 years. COP/DET/FUS proteins are well-conserved, and regulate a variety of biological processes in plants and animals. The fact that these proteins contribute to the repression of plant photomorphogenesis by regulating the ubiquitin-proteasome-dependent pathway has been well established. Recently, molecular insight has been gained into the functional diversity of COP/DET/FUS. Here, we review the current research on the roles of COP/DET/FUS, with a focus on the functional conversion of COP1 in photomorphogenesis.