title: A heterocomplex of iron superoxide dismutases defends chloroplast nucleoids against oxidative stress and is essential for chloroplast development in Arabidopsis.
abstract: There are three iron superoxide dismutases in Arabidopsis thaliana: FE SUPEROXIDE DISMUTASE1 (FSD1), FSD2, and FSD3. Their biological roles in chloroplast development are unknown. Here, we show that FSD2 and FSD3 play essential roles in early chloroplast development, whereas FSD1, which is found in the cytoplasm, does not. An fsd2-1 fsd3-1 double mutant had a severe albino phenotype on agar plates, whereas fsd2 and fsd3 single knockout mutants had pale green phenotypes. Chloroplast development was arrested in young seedlings of the double mutant. The mutant plants were highly sensitive to oxidative stress and developed increased levels of reactive oxygen species (ROS) during extended darkness. The FSD2 and FSD3 proteins formed a heteromeric protein complex in the chloroplast nucleoids. Furthermore, transgenic Arabidopsis plants overexpressing both the FSD2 and FSD3 genes showed greater tolerance to oxidative stress induced by methyl viologen than did the wild type or single FSD2- or FSD3-overexpressing lines. We propose that heteromeric FSD2 and FSD3 act as ROS scavengers in the maintenance of early chloroplast development by protecting the chloroplast nucleoids from ROS.
authors.affiliation: Gene Discovery Research Group, RIKEN Plant Science Center, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
authors.forename: Fumiyoshi
authors.initials: F
authors.lastname: Myouga
authors.forename: Chieko
authors.initials: C
authors.lastname: Hosoda
authors.forename: Taishi
authors.initials: T
authors.lastname: Umezawa
authors.forename: Haruko
authors.initials: H
authors.lastname: Iizumi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuromori
authors.forename: Reiko
authors.initials: R
authors.lastname: Motohashi
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Shono
authors.forename: Noriko
authors.initials: N
authors.lastname: Nagata
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ikeuchi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D009154:Mutation; D018384:Oxidative Stress; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase