title: N-terminal domain-mediated homodimerization is required for photoreceptor activity of Arabidopsis CRYPTOCHROME 1.
abstract: 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.
authors.affiliation: 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.
authors.forename: Yi
authors.initials: Y
authors.lastname: Sang
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Li
authors.forename: Vicente
authors.initials: V
authors.lastname: Rubio
authors.forename: Yan-Chun
authors.initials: YC
authors.lastname: Zhang
authors.forename: Jian
authors.initials: J
authors.lastname: Mao
authors.forename: Xing-Wang
authors.initials: XW
authors.lastname: Deng
authors.forename: Hong-Quan
authors.initials: HQ
authors.lastname: Yang
mesh_terms: 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
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins