N-terminal domain-mediated homodimerization is required for photoreceptor activity of Arabidopsis CRYPTOCHROME 1.
Cryptochromes (CRY) are blue light receptors that share sequence similarity with photolyases, flavoproteins that catalyze the repair of UV light-damaged DNA. Transgenic Arabidopsis thaliana seedlings expressing the C-terminal domains of the Arabidopsis CRY fused to beta-glucuronidase (GUS) display a constitutive photomorphogenic (COP) phenotype, indicating that the signaling mechanism of Arabidopsis CRY is mediated through the C-terminal domain. The role of the Arabidopsis CRY N-terminal photolyase-like domain in CRY action remains poorly understood. Here, we report the essential role of the Arabidopsis CRY1 N-terminal domain (CNT1) in the light activation of CRY1 photoreceptor activity. Yeast two-hybrid assay, in vitro binding, in vivo chemical cross-linking, gel filtration, and coimmunoprecipitation studies indicate that CRY1 homodimerizes in a light-independent manner. Mutagenesis and transgenic studies demonstrate that CNT1-mediated dimerization is required for light activation of the C-terminal domain of CRY1 (CCT1). Transgenic data and native gel electrophoresis studies suggest that multimerization of GUS is both responsible and required for mediating a COP phenotype on fusion to CCT1. These results indicate that the properties of the GUS multimer are analogous to those of the light-modified CNT1 dimer. Irradiation with blue light modifies the properties of the CNT1 dimer, resulting in a change in CCT1, activating CCT1, and eventually triggering the CRY1 signaling pathway.
Sang
Yi
Y
National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Li
Qing-Hua
QH
Rubio
Vicente
V
Zhang
Yan-Chun
YC
Mao
Jian
J
Deng
Xing-Wang
XW
Yang
Hong-Quan
HQ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D056931:Cryptochromes; D019281:Dimerization; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D055537:Light Signal Transduction / Q000235:genetics* / Q000528:radiation effects; D046911:Macromolecular Substances / Q000378:metabolism / Q000528:radiation effects; D009154:Mutation / Q000502:physiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D017434:Protein Structure, Tertiary / Q000502:physiology / Q000528:radiation effects; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction / Q000502:physiology / Q000528:radiation effects
D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins