title: A revised assay for monitoring autophagic flux in Arabidopsis thaliana reveals involvement of AUTOPHAGY-RELATED9 in autophagy.
abstract: Autophagy targets cytoplasmic cargo to a lytic compartment for degradation. Autophagy-related (Atg) proteins, including the transmembrane protein Atg9, are involved in different steps of autophagy in yeast and mammalian cells. Functional classification of core Atg proteins in plants has not been clearly confirmed, partly because of the limited availability of reliable assays for monitoring autophagic flux. By using proUBQ10-GFP-ATG8a as an autophagic marker, we showed that autophagic flux is reduced but not completely compromised in Arabidopsis thaliana atg9 mutants. In contrast, we confirmed full inhibition of autophagic flux in atg7 and that the difference in autophagy was consistent with the differences in mutant phenotypes such as hypersensitivity to nutrient stress and selective autophagy. Autophagic flux is also reduced by an inhibitor of phosphatidylinositol kinase. Our data indicated that atg9 is phenotypically distinct from atg7 and atg2 in Arabidopsis, and we proposed that ATG9 and phosphatidylinositol kinase activity contribute to efficient autophagy in Arabidopsis.
authors.affiliation: Department of Biological Sciences, Pusan National University, Busan 609-735, Korea.
authors.forename: Kwang Deok
authors.initials: KD
authors.lastname: Shin
authors.forename: Han Nim
authors.initials: HN
authors.lastname: Lee
authors.forename: Taijoon
authors.initials: T
authors.lastname: Chung
mesh_terms: D000595:Amino Acid Sequence; D000730:Androstadienes; D017360:Arabidopsis / Q000166:cytology*; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D060365:Chloroplast Proteins; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010641:Phenotype; D000077191:Wortmannin; D044764:Ubiquitin-Activating Enzymes
chemical_list: D000730:Androstadienes; D029681:Arabidopsis Proteins; D000071183:Autophagy-Related Proteins; D060365:Chloroplast Proteins; D008565:Membrane Proteins; D000077191:Wortmannin; C491970:APG7 protein, Arabidopsis; D044764:Ubiquitin-Activating Enzymes; C466979:APG9 protein, Arabidopsis; C435728:TATC protein, Arabidopsis