Almost all life on earth depend on photosynthesis performed by chloroplasts of algae and land plants. Chloroplasts possess their own genomic DNA (cpDNA), which are considered as a relic of the endosymbiotic cyanobacterium. A copy of cpDNA encodes ~200 proteins essential for photosynthesis and biogenesis, and are packaged in DNA-protein complex called chloroplast nucleoids (CPNs), a counterpart of nuclear chromosome. However, little is known about the evolution of CPN structure and the molecular

more »

... mechanism that regulates CPN morphology. To deduce the evolution of CPN structure, we analyzed s of algae and liverwort, and proposed a model that the recurrent modification of organi ation by eukaryotic factors originally related to chromatin organi ation likely have been the driving force for the diversification of s since the early stage of plant evolution. e also investigated sulfite reductase Si , a ma or component of s in land plants, to reveal the molecular basis to bind and bend cpDNA. The combination of in silico and in vivo analysis revealed that C-terminally region of SiR (~50 aa plays a key role to interact and compact cp . urthermore, we identified the novel gene MOC1, which regulates the CPN morphology in algae and land plants. MOC1 encodes the chloroplast-targeted Holliday junction resolvase, suggesting that MOC1 untangles cpDNA tangled via Holliday junctions to segregate chloroplast genome faithfully.