抄録
Phylogenetic relationships between three lineages of the primary photosynthetic eukaryotes (red algae, green plants and glaucophytes) seemed to remain unresolved because previous nuclear multigene phylogenies used the incomplete red algal gene sequences. Recently, we carried out phylogenetic analyses based on a 1525-amino-acid sequence of four concatenated nuclear genes from various lineages of only mitochondria-containing eukaryotes, using complete genome sequences from the red alga Cyanidioschyzon merolae. This study resolved two large monophyletic groups (groups A and B) and the basal group (Amoebozoa). Group A corresponded to the Opisthokonta (Metazoa and Fungi), where as group B included various primary and secondary plastid-containing lineages (euglenoids, heterokonts, and apicomplexans), Ciliophora, Kinetoplastida, and Heterolobosea. The red algae represented the most basal lineage within group B. Since the single event of the plastid primary endosymbiosis was strongly suggested by other data, it was considered that the primary plastid endosymbiosis likely occurred once in the common ancestor of group B, and the primary plastids were subsequently lost in the ancestor(s) of organisms which now lack primary plastids within group B. A new concept of "Plantae" was proposed for phototrophic and nonphototrophic organisms belonging to group B, on the basis of the common history of the primary plastid endosymbiosis.
