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Science. 2017 May 12;356(6338):631-634. doi: 10.1126/science.aan0038.

Holliday junction resolvases mediate chloroplast nucleoid segregation.

Author information

1
Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto 606-8502, Japan.
2
Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan.
3
Department of Life Science, College of Science, Rikkyo (St. Paul's) University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
4
Department of Frontier Bioscience, Hosei University, Tokyo 184-8584, Japan.
5
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
6
Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan.
7
Department of Biological Sciences, School and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan.
8
Department of Chemical and Biological Science, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681, Japan.
9
Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto 606-8502, Japan. yoshiki@pmg.bot.kyoto-u.ac.jp.

Abstract

Holliday junctions, four-stranded DNA structures formed during homologous recombination, are disentangled by resolvases that have been found in prokaryotes and eukaryotes but not in plant organelles. Here, we identify monokaryotic chloroplast 1 (MOC1) as a Holliday junction resolvase in chloroplasts by analyzing a green alga Chlamydomonas reinhardtii mutant defective in chloroplast nucleoid (DNA-protein complex) segregation. MOC1 is structurally similar to a bacterial Holliday junction resolvase, resistance to ultraviolet (Ruv) C, and genetically conserved among green plants. Reduced or no expression of MOC1 in Arabidopsis thaliana leads to growth defects and aberrant chloroplast nucleoid segregation. In vitro biochemical analysis and high-speed atomic force microscopic analysis revealed that A. thaliana MOC 1 (AtMOC1) binds and cleaves the core of Holliday junctions symmetrically. MOC1 may mediate chloroplast nucleoid segregation in green plants by resolving Holliday junctions.

PMID:
28495749
DOI:
10.1126/science.aan0038
[Indexed for MEDLINE]

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