Arabidopsis cryptochrome 1 undergoes COP1 and LRBs-dependent degradation in response to high blue light.

Arabidopsis cryptochrome 1 (CRY1) is an important blue light photoreceptor that promotes photomorphogenesis under blue light. The blue light photoreceptors CRY2 and phototropin 1, and the red/far-red light photoreceptors phytochromes B and A undergo degradation in response to blue and red light, respectively. This study investigated whether and how CRY1 might undergo degradation in response to high-intensity blue light (HBL). We demonstrated that CRY1 is ubiquitinated and degraded through the 26S proteasome pathway in response to HBL. We found that the E3 ubiquitin ligase constitutive photomorphogenic 1 (COP1) is involved in mediating HBL-induced ubiquitination and degradation of CRY1. We also found that the E3 ubiquitin ligases LRBs physically interact with CRY1 and are also involved in mediating CRY1 ubiquitination and degradation in response to HBL. We further demonstrated that blue-light inhibitor of cryptochromes 1 interacts with CRY1 in a blue-light-dependent manner to inhibit CRY1 dimerization/oligomerization, leading to the repression of HBL-induced degradation of CRY1. Our findings indicate that the regulation of CRY1 stability in HBL is coordinated by COP1 and LRBs, which provides a mechanism by which CRY1 attenuates its own signaling and optimizes photomorphogenesis under HBL.