The group led by Yusuke Kobayashi, a doctoral student at the Graduate School of Science, Kyoto University, and Yoshiki Nishimura, is a group of chloroplasts in collaboration with Yamaguchi University, Tokyo Institute of Technology, Hosei University, Rikkyo University, and Japan Women's University. We discovered the gene MOC1 that regulates the distribution (inheritance) of "chloroplast DNA (chloroplast nucleus-like body)" and the chloroplast-type holiday junction dissociation enzyme encoded by this gene.
In the chloroplast, which is the site of photosynthesis, DNA is folded by various proteins to form a "nucleoid".Chloroplast nucleoid replication and distribution precedes chloroplast division.Nucleoid replication, division, and distribution (heredity) are essential elements for the maintenance of photosynthesis and the survival of plants, but the mechanism of their control was unknown.
Using the unicellular green alga Chlamydomonas, the research group isolated a "moc variant" with an abnormal chloroplast nucleoid shape, and discovered an unknown gene called MOC1 in the process of identifying the causative gene.This gene is also widely conserved in land plants.Biochemical analysis shows that this protein binds to the center of the Holliday junction, a structure that appears during homologous recombination during DNA damage repair, replication, and meiosis, and cuts the structure accurately. It was revealed that it is a chlorophyll-type Holliday junction dissociative enzyme.
Furthermore, by combining "DNA origami (a technology that can design various structures by combining long and short DNA strands)" and atomic force microscopy technology, we observed how the Holliday junction was cut.As a result, we succeeded in clearly capturing how the MOC1 protein binds to the central part of the Holliday junction and cleaves.
From this basic discovery, it is expected that the mechanism of homologous recombination in chloroplasts will be elucidated, and that it will be applied to applied research for the production of new substances.
Paper information:[Science] Holliday junction resolvases mediate chloroplast nucleoid segregation
