Ubiquitin facilitates a quality-control pathway that removes damaged chloroplasts

Science. 2015 Oct 23;350(6259):450-4. doi: 10.1126/science.aac7444. Epub 2015 Oct 22.


Energy production by chloroplasts and mitochondria causes constant oxidative damage. A functioning photosynthetic cell requires quality-control mechanisms to turn over and degrade chloroplasts damaged by reactive oxygen species (ROS). Here, we generated a conditionally lethal Arabidopsis mutant that accumulated excess protoporphyrin IX in the chloroplast and produced singlet oxygen. Damaged chloroplasts were subsequently ubiquitinated and selectively degraded. A genetic screen identified the plant U-box 4 (PUB4) E3 ubiquitin ligase as being necessary for this process. pub4-6 mutants had defects in stress adaptation and longevity. Thus, we have identified a signal that leads to the targeted removal of ROS-overproducing chloroplasts.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Physiological / genetics
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis / ultrastructure
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Chloroplasts / metabolism*
  • Genes, Lethal
  • Metabolic Networks and Pathways
  • Mitochondria / metabolism
  • Mutation
  • Oxidative Stress*
  • Photosynthesis
  • Singlet Oxygen / metabolism*
  • Stress, Physiological / genetics
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination


  • Arabidopsis Proteins
  • Ubiquitin
  • Singlet Oxygen
  • Ubiquitin-Protein Ligases
  • PUB4 protein, Arabidopsis

Associated data

  • GEO/GSE71764