Direct interaction of Arabidopsis cryptochromes with COP1 in light controldevelopment

Arabidopsis seedling photomorphogenesis involves two antagonistically actin g components, COP1 and HY5. COP1 specifically targets HY5 for degradation v ia the 26S proteasome in the dark through their direct physical interaction . Little is known regarding how light signals perceived by photoreceptors a re transduced to regulate COP1. Arabidopsis has two related cryptochromes ( cry1 and cry2) mediating various blue/ultraviolet-A light responses. Here w e show that both photoactivated cryptochromes repress COP1 activity through a direct protein-protein contact and that this direct regulation is primar ily responsible for the cryptochrome-mediated blue light regulation of seed ling photomorphogenic development and genome expression profile.