Regulation of Arabidopsis cryptochrome 2 by blue-light-dependent phosphorylation

Abstract

Cryptochromes are blue/ultraviolet-A light receptors that mediate various light responses in plants and animals^1,2. But the initial photochemical reaction of cryptochrome is still unclear. For example, although most photoreceptors are known to undergo light-dependent protein modification such as phosphorylation^3,4, no blue-light dependent phosphorylation has been reported for a cryptochrome. Arabidopsis cryptochrome 2 (cry2) mediates light regulation of seedling development and photoperiodic flowering^5,6. The physiological activity and cellular level of cry2 protein are light-dependent^5,6,7,8, and protein–protein interactions are important for cry2 function^9,10. Here we report that cry2 undergoes a blue-light-dependent phosphorylation, and that cry2 phosphorylation is associated with its function and regulation. Our results suggest that, in the absence of light, cry2 remains unphosphorylated, inactive and stable; absorption of blue light induces the phosphorylation of cry2, triggering photomorphogenic responses and eventually degradation of the photoreceptor.