title: The Arabidopsis B-box protein BZS1/BBX20 interacts with HY5 and mediates strigolactone regulation of photomorphogenesis.
abstract: Plant growth is controlled by integration of hormonal and light-signaling pathways. BZS1 is a B-box zinc finger protein previously characterized as a negative regulator in the brassinosteroid (BR)-signaling pathway and a positive regulator in the light-signaling pathway. However, the mechanisms by which BZS1/BBX20 integrates light and hormonal pathways are not fully understood. Here, using a quantitative proteomic workflow, we identified several BZS1-associated proteins, including light-signaling components COP1 and HY5. Direct interactions of BZS1 with COP1 and HY5 were verified by yeast two-hybrid and co-immunoprecipitation assays. Overexpression of BZS1 causes a dwarf phenotype that is suppressed by the hy5 mutation, while overexpression of BZS1 fused with the SRDX transcription repressor domain (BZS1-SRDX) causes a long-hypocotyl phenotype similar to hy5, indicating that BZS1's function requires HY5. BZS1 positively regulates HY5 expression, whereas HY5 negatively regulates BZS1 protein level, forming a feedback loop that potentially contributes to signaling dynamics. In contrast to BR, strigolactone (SL) increases BZS1 level, whereas the SL responses of hypocotyl elongation, chlorophyll and HY5 accumulation are diminished in the BZS1-SRDX seedlings, indicating that BZS1 is involved in these SL responses. These results demonstrate that BZS1 interacts with HY5 and plays a central role in integrating light and multiple hormone signals for photomorphogenesis in Arabidopsis.
authors: Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, China; Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA.
authors: Chuang-Qi
authors: CQ
authors: Wei
authors: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA.
authors: Chih-Wei
authors: CW
authors: Chien
authors: Hebei Entry-Exit Inspection and Quarantine Bureau of the People's Republic of China, Shijiazhuang 050051, China.
authors: Lian-Feng
authors: LF
authors: Ai
authors: Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, China.
authors: Jun
authors: J
authors: Zhao
authors: Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, China; Center of Basic Forestry and Proteomics, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
authors: Zhenzhen
authors: Z
authors: Zhang
authors: Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
authors: Kathy H
authors: KH
authors: Li
authors: Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
authors: Alma L
authors: AL
authors: Burlingame
authors: Key Laboratory of Molecular and Cellular Biology of Ministry of Education, Hebei Collaboration Innovation Center for Cell Signaling, Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, China. Electronic address: yusun05@hebtu.edu.cn.
authors: Yu
authors: Y
authors: Sun
authors: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA. Electronic address: zywang24@stanford.edu.
authors: Zhi-Yong
authors: ZY
authors: Wang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D006575:Heterocyclic Compounds, 3-Ring / Q000378:metabolism*; D007783:Lactones / Q000378:metabolism*; D008027:Light; D009687:Nuclear Proteins / Q000378:metabolism*; D063245:Plant Development / Q000528:radiation effects*; D011485:Protein Binding / Q000528:radiation effects; D015398:Signal Transduction / Q000528:radiation effects; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C574877:At4g39070 protein, Arabidopsis; D050976:Basic-Leucine Zipper Transcription Factors; C000591191:GR24 strigolactone; C109254:HY5 protein, Arabidopsis; D006575:Heterocyclic Compounds, 3-Ring; D007783:Lactones; D009687:Nuclear Proteins; D014157:Transcription Factors
keywords: BZS1/BBX20; COP1; HY5; Immunoprecipitation; Light signaling; Mass spectrometry; Strigolactone