title: Formation and dissociation of the BSS1 protein complex regulates plant development via brassinosteroid signaling.
abstract: Brassinosteroids (BRs) play important roles in plant development and the response to environmental cues. BIL1/BZR1 is a master transcription factor in BR signaling, but the mechanisms that lead to the finely tuned targeting of BIL1/BZR1 by BRs are unknown. Here, we identified BRZ-SENSITIVE-SHORT HYPOCOTYL1 (BSS1) as a negative regulator of BR signaling in a chemical-biological analysis involving brassinazole (Brz), a specific BR biosynthesis inhibitor. The bss1-1D mutant, which overexpresses BSS1, exhibited a Brz-hypersensitive phenotype in hypocotyl elongation. BSS1 encodes a BTB-POZ domain protein with ankyrin repeats, known as BLADE ON PETIOLE1 (BOP1), which is an important regulator of leaf morphogenesis. The bss1-1D mutant exhibited an increased accumulation of phosphorylated BIL1/BZR1 and a negative regulation of BR-responsive genes. The number of fluorescent BSS1/BOP1-GFP puncta increased in response to Brz treatment, and the puncta were diffused by BR treatment in the root and hypocotyl. We show that BSS1/BOP1 directly interacts with BIL1/BZR1 or BES1. The large protein complex formed between BSS1/BOP1 and BIL1/BZR1 was only detected in the cytosol. The nuclear BIL1/BZR1 increased in the BSS1/BOP1-deficient background and decreased in the BSS1/BOP1-overexpressing background. Our study suggests that the BSS1/BOP1 protein complex inhibits the transport of BIL1/BZR1 to the nucleus from the cytosol and negatively regulates BR signaling.
authors: Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Kanagawa 230-0045, Japan.
authors: Setsuko
authors: S
authors: Shimada
authors: Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Saiwai-Cho, Fuchu, Tokyo 183-8509, Japan.
authors: Tomoyuki
authors: T
authors: Komatsu
authors: Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
authors: Ayumi
authors: A
authors: Yamagami
authors: RIKEN Genome Science Center, Tsurumi, Yokohama, Kanagawa 230-0045, Japan.
authors: Miki
authors: M
authors: Nakazawa
authors: Synthetic Genomics Research Team, Biomass Engineering Program Cooperation Division, RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Kanagawa 230-0045, Japan.
authors: Minami
authors: M
authors: Matsui
authors: United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Saiwai-Cho, Fuchu, Tokyo 183-8509, Japan.
authors: Hiroshi
authors: H
authors: Kawaide
authors: United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Saiwai-Cho, Fuchu, Tokyo 183-8509, Japan.
authors: Masahiro
authors: M
authors: Natsume
authors: Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan RIKEN Center for Sustainable Resource Science, Wako, Saitama 351-0198, Japan.
authors: Hiroyuki
authors: H
authors: Osada
authors: Department of Applied Biological Chemistry, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
authors: Tadao
authors: T
authors: Asami
authors: Antibiotics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan RIKEN Center for Sustainable Resource Science, Wako, Saitama 351-0198, Japan Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan tnakano@riken.jp.
authors: Takeshi
authors: T
authors: Nakano
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism* / Q000494:pharmacology; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D063245:Plant Development / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014230:Triazoles / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; C496963:BOP1 protein, Arabidopsis; D060406:Brassinosteroids; D046912:Multiprotein Complexes; D012333:RNA, Messenger; D014230:Triazoles; D049452:Green Fluorescent Proteins; C412342:brassinazole