N-Terminal Domain-Mediated Homodimerization Is Required for Photoreceptor Activity of Arabidopsis CRYPTOCHROME 1

• Published in: The Plant cell 2005-05, Vol.17 (5), p.1569-1584
• Main Authors: Sang, Yi, Li, Qing-Hua, Rubio, Vicente, Zhang, Yan-Chun, Mao, Jian, Deng, Xing-Wang, Yang, Hong-Quan
• Format: Article
• Language: English
• Subjects: Antibodies; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis - radiation effects; Arabidopsis Proteins; Arabidopsis thaliana; beta-glucuronidase; blue light; cryptochrome; Cryptochromes; Dimerization; Dimers; Flavoproteins - genetics; Flavoproteins - metabolism; Flavoproteins - radiation effects; Gels; homodimerization; Irradiation; Light; Light Signal Transduction - genetics; Light Signal Transduction - radiation effects; Macromolecular Substances - metabolism; Macromolecular Substances - radiation effects; multimerization; Mutation - physiology; Phenotypes; Photoreceptors; Photosynthetic Reaction Center Complex Proteins - genetics; Photosynthetic Reaction Center Complex Proteins - metabolism; Photosynthetic Reaction Center Complex Proteins - radiation effects; phytochrome; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Plants, Genetically Modified - radiation effects; promoter regions; Protein Structure, Tertiary - physiology; Protein Structure, Tertiary - radiation effects; protein-protein interactions; Proteins; reporter genes; seedling growth; Seedlings; Seedlings - genetics; Seedlings - metabolism; Seedlings - radiation effects; signal transduction; Signal Transduction - physiology; Signal Transduction - radiation effects; Transgenic plants; Ultraviolet radiation; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.104.029645

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 {szligbeta}-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.