title: Arabidopsis cotyledon-specific chloroplast biogenesis factor CYO1 is a protein disulfide isomerase.
abstract: Chloroplast development in cotyledons differs in a number of ways from that in true leaves, but the cotyledon-specific program of chloroplast biogenesis has not been clarified. The cyo1 mutant in Arabidopsis thaliana has albino cotyledons but normal green true leaves. Chloroplasts develop abnormally in cyo1 mutant plants grown in the light, but etioplasts are normal in mutants grown in the dark. We isolated CYO1 by T-DNA tagging and verified that the mutant allele was responsible for the albino cotyledon phenotype by complementation. CYO1 has a C(4)-type zinc finger domain similar to that of Escherichia coli DnaJ. CYO1 is expressed mainly in young plants under light conditions, and the CYO1 protein localizes to the thylakoid membrane in chloroplasts. Transcription of nuclear photosynthetic genes is generally unaffected by the cyo1 mutation, but the level of photosynthetic proteins is decreased in cyo1 mutants. Recombinant CYO1 accelerates disulfide bond reduction in the model substrate insulin and renatures RNase A, indicating that CYO1 has protein disulfide isomerase activity. These results suggest that CYO1 has a chaperone-like activity required for thylakoid biogenesis in cotyledons.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. hshimada@bio.titech.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimada
authors.forename: Mariko
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Kan
authors.initials: K
authors.lastname: Ogura
authors.forename: John E
authors.initials: JE
authors.lastname: Froehlich
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Osteryoung
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Shirano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shibata
authors.forename: Shinji
authors.initials: S
authors.lastname: Masuda
authors.forename: Kazuki
authors.initials: K
authors.lastname: Mori
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Takamiya
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D018548:Cotyledon / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D015151:Immunoblotting; D046529:Microscopy, Electron, Transmission; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D019704:Protein Disulfide-Isomerases