title: CUL4 forms an E3 ligase with COP1 and SPA to promote light-induced degradation of PIF1.
abstract: Plants undergo contrasting developmental programs in dark and light. Photomorphogenesis, a light-adapted programme is repressed in the dark by the synergistic actions of CUL4(COP1-SPA) E3 ubiquitin ligase and a subset of basic helix-loop-helix transcription factors called phytochrome interacting factors (PIFs). To promote photomorphogenesis, light activates the phytochrome family of sensory photoreceptors, which inhibits these repressors by poorly understood mechanisms. Here, we show that the CUL4(COP1-SPA) E3 ubiquitin ligase is necessary for the light-induced degradation of PIF1 in Arabidopsis. The light-induced ubiquitylation and subsequent degradation of PIF1 is reduced in the cop1, spaQ and cul4 backgrounds. COP1, SPA1 and CUL4 preferentially form complexes with the phosphorylated forms of PIF1 in response to light. The cop1 and spaQ seeds display strong hyposensitive response to far-red light-mediated seed germination and light-regulated gene expression. These data show a mechanism by which an E3 ligase attenuates its activity by degrading its cofactor in response to light.
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Bu
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Xiaosa
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Inyup
authors.initials: I
authors.lastname: Paik
authors.affiliation: Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Huang
authors.affiliation: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), Biocenter, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Hoecker
authors.affiliation: Peking-Yale Joint Center for Plant Molecular Genetics and Agro-Biotechnology, State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, School of Advanced Agriculture Sciences and School of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Enamul
authors.identifier: http://orcid.org/0000-0001-7692-5139
authors.initials: E
authors.lastname: Huq
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics*; D044842:Cullin Proteins / Q000235:genetics*; D018525:Germination / Q000235:genetics*; D015151:Immunoblotting; D008027:Light; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D012333:RNA, Messenger; D044767:Ubiquitin-Protein Ligases; C514806:CULLIN4 protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis; C118571:SPA1 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis