クロララクニオン藻の二次色素体の進化 Secondary plastid evolution of chlorarachniophyte algae
Plastids (chloroplasts) have been evolved by multiple endosymbiotic events between a non-photosynthetic protist and a photosynthetic organism. Plants and a part of algae (green and red algae) acquired plastids from a cyanobacterium through a primary endosymbiosis, and many other algal groups have more complex plastids originated from green or red algal endosymbionts via secondary endosymbioses. In these events, many genes residing in the endosymbiont genomes have been transferred to the host nuclear genomes, and bulk of which encode proteins that are targeted back to plastids across multiple membranes. Plastid targeting of nucleus-encoded proteins is essential to maintain and control an endosymbiont as a photosynthetic organelle. Chlorarachniophytes are an algal group possessing extremely complex plastids acquired by the uptake of green algal endosymbiont. Four membrane surround the plastids and a relict nucleus, called the nucleomorph, of the endosymbiont exists in the periplastidal compartment. This review summarizes current studies on protein targeting into complex plastids of chlorarachniophytes and reductive evolution of the endosymbiotically-derived nucleomorph genomes.
原生動物学雑誌 48(1-2), 57-65, 2015