Cryptochrome 1 promotes photomorphogenesis in Arabidopsis by displacing substrates from the COP1 ubiquitin ligase.

In blue light, cryptochrome photoreceptors inhibit the key repressor of light signaling, the COP1/SPA ubiquitin ligase, to promote photomorphogenic responses. This inhibition relies on the direct interaction between COP1 and cryptochromes. Here, we analyzed the molecular mechanism of CRY1-mediated inhibition of COP1.