title: Protein aggregates are transported to vacuoles by a macroautophagic mechanism in nutrient-starved plant cells.
abstract: When a fusion protein of cytochrome b5 (Cyt b5) and the red fluorescent protein (RFP) are expressed in tobacco BY-2 cells, the expressed protein forms intracellular aggregates that emit red fluorescence. When such cells are grown to the stationary phase or incubated in nutrient limited medium, RFP fluorescence can be detected in the vacuolar lumen. We investigated this transport mechanism using a limited-nitrogen model. E-64 and 3-methyladenine, which inhibit autophagic processes, blocked the transport of the RFP signal to the vacuole. We next traced the autophagic process in tobacco cells using YFP fused with the tobacco Atg8 homologue (YFP-NtAtg8) and analyzed the contribution of autophagy to the vacuolar transport of the aggregates. Under limited-nitrogen conditions, the aggregates were degraded in preference to other organelles, and the autophagosomes colocalized with the aggregates at a higher frequency than with mitochondria. This is the first demonstration that selective macroautophagic degradation can occur in plant cells.
authors.affiliation: RIKEN Plant Science Center, Tsurumi-ku, Yokohama, Japan.
authors.forename: Kiminori
authors.initials: K
authors.lastname: Toyooka
authors.forename: Yuji
authors.initials: Y
authors.lastname: Moriyasu
authors.forename: Yumi
authors.initials: Y
authors.lastname: Goto
authors.forename: Masaki
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Hiroo
authors.initials: H
authors.lastname: Fukuda
authors.forename: Ken
authors.initials: K
authors.lastname: Matsuoka
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000071190:Autophagy-Related Protein 8 Family; D002460:Cell Line; D015786:Cytochromes b5 / Q000235:genetics / Q000378:metabolism*; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008928:Mitochondria / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D013217:Starvation; D014026:Nicotiana / Q000502:physiology*; D014617:Vacuoles / Q000502:physiology* / Q000648:ultrastructure
chemical_list: C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C025946:3-methyladenine; D015786:Cytochromes b5; D007930:Leucine; D000225:Adenine; D009584:Nitrogen; C024974:E 64