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Updated: Mar 2, 2026

Single-Molecule Förster Resonance Energy Transfer Methods for Real-Time Investigation of the Holliday Junction Resolution by GEN1
Published on: September 18, 2019
Holliday junction resolvases mediate chloroplast nucleoid segregation
Yusuke Kobayashi1, Osami Misumi2, Masaki Odahara3
1Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto 606-8502, Japan.
Researchers identified monokaryotic chloroplast 1 (MOC1) as a crucial Holliday junction resolvase in plant chloroplasts. This discovery explains how chloroplast DNA is segregated, impacting plant growth and development.
Area of Science:
- Molecular Biology
- Plant Science
- Genetics
Background:
- Holliday junctions are key DNA structures in homologous recombination.
- Resolvases disentangle Holliday junctions in prokaryotes and eukaryotes.
- Plant organelles lacked identified Holliday junction resolvases until now.
Purpose of the Study:
- To identify the Holliday junction resolvase in plant chloroplasts.
- To investigate the role of MOC1 in chloroplast nucleoid segregation.
- To understand the mechanism of MOC1 in green plants.
Main Methods:
- Analysis of a *Chlamydomonas reinhardtii* mutant lacking chloroplast nucleoid segregation.
- Genetic analysis of *MOC1* conservation and expression in *Arabidopsis thaliana*.
- In vitro biochemical and high-speed atomic force microscopy analyses of AtMOC1 activity.
Main Results:
- *MOC1* was identified as a chloroplast Holliday junction resolvase.
- Reduced *MOC1* expression in *Arabidopsis thaliana* caused growth defects and aberrant chloroplast nucleoid segregation.
- AtMOC1 binds and cleaves Holliday junctions symmetrically at their core.
Conclusions:
- MOC1 is a conserved Holliday junction resolvase in green plant chloroplasts.
- MOC1 plays a vital role in chloroplast nucleoid segregation.
- MOC1-mediated Holliday junction resolution is essential for plant development.
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