An Arabidopsis SUMO E3 Ligase, SIZ1, Negatively Regulates Photomorphogenesis by Promoting COP1 Activity

Xiao Li Lin, De Niu, Zi Liang Hu, Dae Heon Kim, Yin Hua Jin, Bin Cai, Peng Liu, Kenji Miura, Dae Jin Yun, Woe Yeon Kim, Rongcheng Lin, Jing Bo Jin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), a ubiquitin E3 ligase, is a central negative regulator of photomorphogenesis. However, how COP1 activity is regulated by post-translational modifications remains largely unknown. Here we show that SUMO (small ubiquitin-like modifier) modification enhances COP1 activity. Loss-of-function siz1 mutant seedlings exhibit a weak constitutive photomorphogenic phenotype. SIZ1 physically interacts with COP1 and mediates the sumoylation of COP1. A K193R substitution in COP1 blocks its SUMO modification and reduces COP1 activity in vitro and in planta. Consistently, COP1 activity is reduced in siz1 and the level of HY5, a COP1 target protein, is increased in siz1. Sumoylated COP1 may exhibits higher transubiquitination activity than does non-sumoylated COP1, but SIZ1-mediated SUMO modification does not affect COP1 dimerization, COP1-HY5 interaction, and nuclear accumulation of COP1. Interestingly, prolonged light exposure reduces the sumoylation level of COP1, and COP1 mediates the ubiquitination and degradation of SIZ1. These regulatory mechanisms may maintain the homeostasis of COP1 activity, ensuing proper photomorphogenic development in changing light environment. Our genetic and biochemical studies identify a function for SIZ1 in photomorphogenesis and reveal a novel SUMO-regulated ubiquitin ligase, COP1, in plants.

Original languageEnglish (US)
Article numbere1006016
JournalPLOS Genetics
Issue number4
StatePublished - Apr 2016

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics
  • Genetics(clinical)
  • Cancer Research


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