2018 Volume 30 Issue 1 Pages 73-81
Chloroplasts possess ~100 copies of their own DNA (chloroplast DNA: cpDNA) that are packaged into chloroplast nucleoids, cpDNA-protein complexes. For the faithful segregation of gigantic genomic DNA molecules, Holliday junctions, four-stranded DNA structures formed during homologous recombination, are required to be disentangled prior to the division. Holliday junction is resolved with resolvases which have been identified in prokaryotes and eukaryotes but not in chloroplasts. We first identified Monokaryotic chloroplast 1 (MOC1) as a Holliday junction resolvase in chloroplasts by the analysis of a green alga Chlamydomonas reinhardtii mutant defective in chloroplast nucleoid segregation. MOC1s are crucial for the chloroplast nucleoid segregation and cpDNA maintenance across a wide range of green plants. Here we trace the history of Holliday junction study by focusing on the significance of our finding of the Holliday junction resolvases in chloroplasts.
