| description |
Paulinella micropora is a freshwater-living rhizarian amoeba possessing a unique blue-green photosynthetic organelle, termed as cyanelle, derived from an endosymbiotic cyanobacterium. Interestingly, the ancestral cyanobacterium of this cyanelle was phylogenetically distinct form that of the plants and algal chloroplasts, and P. micropora is thought to have obtained the cyanobacterial endosymbiont about 60 million years ago, which event was far more recent than the endosymbiosis event of the chloroplast's ancestor more than 1000 million years ago. The cyanelle retains peptide-glycan layer that is the remnant of endosymbiont's cell wall, and its genome size is about 1Mb, which is the intermediate size between the genomes of chloroplasts and free-living cyanobacteria. Thus it has been thought that the cyanelle should be a primitive plastid, and that P. micropora is a unique organism on the way of early plastid evolution. In our project, to elucidate how the cyanobacterial endosymbiont genes had been transferred to the host nucleus, and how the transferred genes had acquired the eukaryotic promoters functional in the nuclear gnome, we performed the whole genome sequencing, RNA-seq analysis, and transcription start site (TSS)-analysis of P. micropora, providing novel insights into the genome and the promoter architecture of the organism in the early phase of primary endosymbiotic evolution. |