Ubiquitin facilitates a quality-control pathway that removes damaged chloroplasts.
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.
Plant Biology Laboratory, The Salk Institute, La Jolla, CA.
Jesse D
JD
Woodson
Waitt Advanced Biophotonics Center, The Salk Institute, La Jolla, CA.
Matthew S
MS
Joens
Plant Biology Laboratory, The Salk Institute, La Jolla, CA. Division of Biological Sciences, University of California-San Diego, La Jolla, CA.
Andrew B
AB
Sinson
Plant Biology Laboratory, The Salk Institute, La Jolla, CA. Howard Hughes Medical Institute, The Salk Institute, La Jolla, CA.
Jonathan
J
Gilkerson
Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
Patrice A
PA
Salomé
Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
Detlef
D
Weigel
Waitt Advanced Biophotonics Center, The Salk Institute, La Jolla, CA.
James A
JA
Fitzpatrick
Plant Biology Laboratory, The Salk Institute, La Jolla, CA. Howard Hughes Medical Institute, The Salk Institute, La Jolla, CA. chory@salk.edu.
Joanne
J
Chory
D000222:Adaptation, Physiological / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D005804:Genes, Lethal; D053858:Metabolic Networks and Pathways; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D018384:Oxidative Stress; D010788:Photosynthesis; D026082:Singlet Oxygen / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
D029681:Arabidopsis Proteins; D025801:Ubiquitin; D026082:Singlet Oxygen; D044767:Ubiquitin-Protein Ligases; C000596069:PUB4 protein, Arabidopsis