title: Highly oxidized peroxisomes are selectively degraded via autophagy in Arabidopsis.
abstract: The positioning of peroxisomes in a cell is a regulated process that is closely associated with their functions. Using this feature of the peroxisomal positioning as a criterion, we identified three Arabidopsis thaliana mutants (peroxisome unusual positioning1 [peup1], peup2, and peup4) that contain aggregated peroxisomes. We found that the PEUP1, PEUP2, and PEUP4 were identical to Autophagy-related2 (ATG2), ATG18a, and ATG7, respectively, which are involved in the autophagic system. The number of peroxisomes was increased and the peroxisomal proteins were highly accumulated in the peup1 mutant, suggesting that peroxisome degradation by autophagy (pexophagy) is deficient in the peup1 mutant. These aggregated peroxisomes contained high levels of inactive catalase and were more oxidative than those of the wild type, indicating that peroxisome aggregates comprise damaged peroxisomes. In addition, peroxisome aggregation was induced in wild-type plants by exogenous application of hydrogen peroxide. The cat2 mutant also contained peroxisome aggregates. These findings demonstrate that hydrogen peroxide as a result of catalase inactivation is the inducer of peroxisome aggregation. Furthermore, an autophagosome marker, ATG8, frequently colocalized with peroxisome aggregates, indicating that peroxisomes damaged by hydrogen peroxide are selectively degraded by autophagy in the wild type. Our data provide evidence that autophagy is crucial for quality control mechanisms for peroxisomes in Arabidopsis.
authors.affiliation: Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors.forename: Michitaro
authors.initials: M
authors.lastname: Shibata
authors.forename: Kazusato
authors.initials: K
authors.lastname: Oikawa
authors.forename: Kohki
authors.initials: K
authors.lastname: Yoshimoto
authors.forename: Maki
authors.initials: M
authors.lastname: Kondo
authors.forename: Shoji
authors.initials: S
authors.lastname: Mano
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamada
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.forename: Wataru
authors.initials: W
authors.lastname: Sakamoto
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: Mikio
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology; D001343:Autophagy; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism / Q000502:physiology; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D006861:Hydrogen Peroxide; C490276:CAT2 protein, Arabidopsis