ANALYSIS OF THE CLUSTER OF RIBOSOMAL-PROTEIN GENES IN THE PLASTID GENOME OF A UNICELLULAR RED ALGA CYANIDIOSCHYZON MEROLAE - TRANSLOCATION OF THE STR CLUSTER AS AN EARLY EVENT IN THE RHODOPHYTE-CHROMOPHYTE LINEAGE OF PLASTID EVOLUTION

The nucleotide sequence of a cluster of ribosomal protein genes in the plastid genome of a unicellular red alga, Cyanidioschyzon merolae, wh ich has been supposed to be the most primitive alga, was determined. T he phylogenetic tree inferred from the amino acid sequence of ribosoma l proteins of two rhodophytes, a chromophyte, a glaucophyte, two chlor ophytes (land plants), a cyanobacterium, and three eubacteria suggeste d a close relationship between the cyanobacterium Synechocystis PCC680 3 and the plastids of various species in the kingdom Plantae, which is consistent with the hypothesis of the endosymbiotic origin of plastid s. In this tree, the two species of rhodophytes were grouped with the chromophyte, and the glaucophyte was grouped with the chlorophytes. An alysis of the organization of the genes encoding the ribosomal protein s suggested that the translocation of the str cluster occurred early i n the lineage of rhodophytes and chromophytes after these groups had b een separated from chlorophytes and glaucophytes.