title: BZS1, a B-box protein, promotes photomorphogenesis downstream of both brassinosteroid and light signaling pathways.
abstract: Photomorphogenesis is controlled by multiple signaling pathways, including the light and brassinosteroid (BR) pathways. BR signaling activates the BZR1 transcription factor, which is required for suppressing photomorphogenesis in the dark. We identified a suppressor of the BR hypersensitive mutant bzr1-1D and named it bzr1-1D suppressor1-Dominant (bzs1-D). The bzs1-D mutation was caused by overexpression of a B-box zinc finger protein BZS1, which is transcriptionally repressed by BZR1. Overexpression of BZS1 causes de-etiolation in the dark, short hypocotyls in the light, reduced sensitivity to BR treatment, and repression of many BR-activated genes. Knockdown of BZS1 by co-suppression partly suppressed the short hypocotyl phenotypes of BR-deficient or insensitive mutants. These results support that BZS1 is a negative regulator of BR response. BZS1 overexpressors are hypersensitive to different wavelengths of light and loss of function of BZS1 reduces plant sensitivity to light and partly suppresses the constitutive photomorphogenesis 1 (cop1) mutant in the dark, suggesting a positive role in light response. BZS1 protein accumulates at an increased level after light treatment of dark-grown BZS1-OX plants and in the cop1 mutants, and BZS1 interacts with COP1 in vitro, suggesting that light regulates BZS1 through COP1-mediated ubiquitination and proteasomal degradation. These results demonstrate that BZS1 mediates the crosstalk between BR and light pathways.
authors.affiliation: Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Xi-Ying
authors.initials: XY
authors.lastname: Fan
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Dong-Mei
authors.initials: DM
authors.lastname: Cao
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Bai
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Luo
authors.forename: Hong-Juan
authors.initials: HJ
authors.lastname: Yang
authors.forename: Chuang-Qi
authors.initials: CQ
authors.lastname: Wei
authors.forename: Sheng-Wei
authors.initials: SW
authors.lastname: Zhu
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
authors.forename: Kang
authors.initials: K
authors.lastname: Chong
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Wang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant / Q000235:genetics; D016153:Genes, Suppressor; D008027:Light; D009024:Morphogenesis / Q000235:genetics / Q000528:radiation effects*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C574877:At4g39070 protein, Arabidopsis; D060406:Brassinosteroids; D014157:Transcription Factors