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Arabidopsis STO/BBX24 negatively regulates UV-B signaling by interacting with COP1 and repressing HY5 transcriptional activity

  • Lei Jiang
  • Yan Wang
  • Qian-Feng Li
  • Lars Olof Björn
  • Jun-Xian He
  • Shao-Shan Li
Publishing year: 2012
Language: English
Pages: 1046-1057
Publication/Series: Cell Research
Volume: 22
Document type: Journal article
Publisher: Science Press

Abstract english

UV-B (280-315 nm) is an integral part of solar radiation and can act either as a stress inducer or as a developmental signal. In recent years, increasing attention has been paid to the low-fluence UV-B-induced photomorphogenic response and several key players in this response have been identified, which include UVR8 (a UV-B-specific photoreceptor), COP1 (a WD40-repeat-containing RING finger protein), HY5 (a basic zipper transcription factor), and RUP1/2 (two UVR8-interacting proteins). Here we report that Arabidopsis SALT TOLERANCE (STO/BBX24), a known regulator for light signaling in plants, defines a new signaling component in UV-B-mediated photomorphogenesis. The bbx24 mutant is hypersensitive to UV-B radiation and becomes extremely dwarfed under UV-B treatment. By contrast, BBX24 overexpression transgenic lines respond much more weakly to UV-B than the bbx24 and wild-type plants.

BBX24 expression is UV-B-inducible and its accumulation under UV-B requires COP1. Co-immunoprecipitation

experiments indicate that BBX24 interacts with COP1 in planta upon UV-B illumination. Moreover, BBX24 interacts

with HY5 and acts antagonistically with HY5 in UV-B-induced inhibition of hypocotyl elongation. Furthermore,

BBX24 attenuates UV-B-induced HY5 accumulation and suppresses its transcription-activation activity. Taken together, our results reveal a previously uncharacterized function of the light-regulated BBX24 in UV-B responses and demonstrate that BBX24 functions as a negative regulator of photomorphogenic UV-B responses by interacting with both COP1 and HY5. The UV-B-inducible expression pattern and its suppression of HY5 activity suggest that BBX24 could be a new component of the feedback regulatory module of UV-B signaling in plants.


  • Biological Sciences
  • Arabidopsis thaliana
  • HY5
  • COP1
  • STO/BBX24
  • photomorphogenesis
  • UV-B


  • Photobiology
  • Photobiology-lup-obsolete
  • ISSN: 1748-7838
Lars Olof Björn
E-mail: lars_olof [dot] bjorn [at] biol [dot] lu [dot] se

Professor emeritus

Molecular Cell Biology

+46 46 222 72 53