Blue-light-dependent interaction of cryptochrome 1 with SPA1 defines a dynamic signaling mechanism

Abstract

Cryptochromes (CRYs) are blue-light photoreceptors that mediate various light responses in plants and animals. The signaling mechanism by which CRYs regulate light responses involves their physical interactions with COP1. Here, we report that CRY1 interacts physically with SPA1 in a blue-light-dependent manner. SPA acts genetically downstream from CRYs to regulate light-controlled development. Blue-light activation of CRY1 attenuates the association of COP1 with SPA1 in both yeast and plant cells. These results indicate that the blue-light-triggered CRY1-SPA1 interaction may negatively regulate COP1, at least in part, by promoting the dissociation of COP1 from SPA1. This interaction and consequent dissociation define a dynamic photosensory signaling mechanism.

Light Signaling, Root Development, and Plasticity

“…The photolyaserelated region binds the chromophore FAD and serves as the light-sensing part. Upon absorbing blue/UV-A light, CRY is phosphorylated and can interact with other protein partners, such as COP1, SPAs, and PIFs (Lian et al, 2011;Liu et al, 2011;Zuo et al, 2011;de Wit et al, 2016;Pedmale et al, 2016).…”

“…COP1 activity relies on physical interaction with SPAs in the COP1/SPA complex. The CRY photoreceptors CRY1 and CRY2, upon blue light activation, can bind to SPAs, and this results in reduced COP1-SPA interaction, leading to stabilization of COP1 targets (Lian et al, 2011;Liu et al, 2011;Zuo et al, 2011). Comparable interaction mechanisms exist between PHYs and SPAs (Zheng et al, 2013;Sheerin et al, 2015), and UVR8 and SPAs (Favory et al, 2009;Huang et al, 2013).…”

Distinct roles of FKF1, GIGANTEA, and ZEITLUPE proteins in the regulation of CONSTANS stability in Arabidopsis photoperiodic flowering

“…Phytochrome B (PHYB) is a red/far-red light photoreceptor that facilitates CO protein degradation in the morning under red-light conditions, whereas PHYA enhances CO protein abundance in the afternoon under LD and far-red-light conditions (5). Cryptochrome 1 (CRY1) and CRY2 are blue-light photoreceptors that interact with SPA1, which in turn sequesters SPA1 from COP1 and then causes enhanced CO stability under blue light (14,15). FKF1 binds to CO through the LOV domain in a blue light-enhanced manner and stabilizes CO specifically in the LD afternoon (6).…”

The Photomorphogenic Signal: An Essential Component of Photoautotrophic Life

“…However, the precise light-mediated mechanism that controls COP1 activity remained unknown until recently. Three simultaneous publications addressed this issue (Lian et al, 2011;Liu et al, 2011;Zuo et al, 2011). They showed that CRY1 interacts with the SPA proteins in a blue-light dependent manner and inhibit the interaction between COP1 and SPA proteins.…”