BLADE-ON-PETIOLE proteins act in an E3 ubiquitin ligase complex to regulate PHYTOCHROME INTERACTING FACTOR 4 abundance

Elife. 2017 Aug 22:6:e26759. doi: 10.7554/eLife.26759.


Both light and temperature have dramatic effects on plant development. Phytochrome photoreceptors regulate plant responses to the environment in large part by controlling the abundance of PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors. However, the molecular determinants of this essential signaling mechanism still remain largely unknown. Here, we present evidence that the BLADE-ON-PETIOLE (BOP) genes, which have previously been shown to control leaf and flower development in Arabidopsis, are involved in controlling the abundance of PIF4. Genetic analysis shows that BOP2 promotes photo-morphogenesis and modulates thermomorphogenesis by suppressing PIF4 activity, through a reduction in PIF4 protein level. In red-light-grown seedlings PIF4 ubiquitination was reduced in the bop2 mutant. Moreover, we found that BOP proteins physically interact with both PIF4 and CULLIN3A and that a CULLIN3-BOP2 complex ubiquitinates PIF4 in vitro. This shows that BOP proteins act as substrate adaptors in a CUL3BOP1/BOP2 E3 ubiquitin ligase complex, targeting PIF4 proteins for ubiquitination and subsequent degradation.

Keywords: A. thaliana; BOP; E3 ligase; PHYB; PIF4; light signalling; plant biology; ubiquitination.

MeSH terms

  • Arabidopsis / growth & development*
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Carrier Proteins / metabolism*
  • Cullin Proteins
  • Gene Expression Regulation, Plant*
  • Light
  • Plant Development / radiation effects
  • Protein Binding
  • Temperature
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination


  • AT1G26830 protein, Arabidopsis
  • Arabidopsis Proteins
  • BOP1 protein, Arabidopsis
  • BOP2 protein, Arabidopsis
  • Basic Helix-Loop-Helix Transcription Factors
  • Carrier Proteins
  • Cullin Proteins
  • PIF4 protein, Arabidopsis
  • Ubiquitin-Protein Ligases

Grants and funding

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.