title: Evidence for contribution of autophagy to rubisco degradation during leaf senescence in Arabidopsis thaliana.
abstract: During leaf senescence, Rubisco is gradually degraded and its components are recycled within the plant. Although Rubisco can be mobilized to the vacuole by autophagy via specific autophagic bodies, the importance of this process in Rubisco degradation has not been shown directly. Here, we monitored Rubisco autophagy during leaf senescence by fusing synthetic green fluorescent protein (sGFP) or monomeric red fluorescent protein (mRFP) with Rubisco in Arabidopsis (Arabidopsis thaliana). When attached leaves were individually exposed to darkness to promote their senescence, the fluorescence of Rubisco-sGFP was observed in the vacuolar lumen as well as chloroplasts. In addition, release of free-sGFP due to the processing of Rubisco-sGFP was observed in the vacuole of individually darkened leaves. This vacuolar transfer and processing of Rubisco-sGFP was not observed in autophagy-deficient atg5 mutants. Unlike sGFP, mRFP was resistant to proteolysis in the leaf vacuole of light-grown plants. The vacuolar transfer and processing of Rubisco-mRFP was observed at an early stage of natural leaf senescence and was also obvious in leaves naturally covered by other leaves. These results indicate that autophagy contributes substantially to Rubisco degradation during natural leaf senescence as well as dark-promoted senescence.
authors.affiliation: Department of Applied Plant Science, Graduate School of Agricultural Sciences, Tohoku University, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ono
authors.forename: Shinya
authors.initials: S
authors.lastname: Wada
authors.forename: Masanori
authors.initials: M
authors.lastname: Izumi
authors.forename: Amane
authors.initials: A
authors.lastname: Makino
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishida
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D001343:Autophagy; D049452:Green Fluorescent Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000502:physiology; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
chemical_list: D049452:Green Fluorescent Proteins; D012273:Ribulose-Bisphosphate Carboxylase