title: Stromal protein degradation is incomplete in Arabidopsis thaliana autophagy mutants undergoing natural senescence.
abstract: BACKGROUND
  Degradation of highly abundant stromal proteins plays an important role in the nitrogen economy of the plant during senescence. Lines of evidence supporting proteolysis within the chloroplast and outside the chloroplast have been reported. Two extra-plastidic degradation pathways, chlorophagy and Rubisco Containing Bodies, rely on cytoplasmic autophagy.
  
  
  RESULTS
  In this work, levels of three stromal proteins (Rubisco large subunit, chloroplast glutamine synthetase and Rubisco activase) and one thylakoid protein (the major light harvesting complex protein of photosystem II) were measured during natural senescence in WT and in two autophagy T-DNA insertion mutants (atg5 and atg7). Thylakoid-localized protein decreased similarly in all genotypes, but stromal protein degradation was incomplete in the two atg mutants. In addition, degradation of two stromal proteins was observed in chloroplasts isolated from mid-senescence leaves.
  
  
  CONCLUSIONS
  These data suggest that autophagy does contribute to the complete proteolysis of stromal proteins, but does not play a major degenerative role. In addition, support for in organello degradation is provided.
authors: Department of Biological Sciences, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, CA 90840-9502, USA.
authors: Travis A
authors: TA
authors: Lee
authors: Scott W
authors: SW
authors: Vande Wetering
authors: Judy A
authors: JA
authors: Brusslan
mesh_terms: D000375:Aging / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001343:Autophagy; D002736:Chloroplasts / Q000378:metabolism; D009154:Mutation; D059748:Proteolysis
chemical_list: D029681:Arabidopsis Proteins