The nucleotide sequence of five ribosomal protein genes from the cyanelles of Cyanophora paradoxa: implications concerning the phylogenetic relationship between cyanelles and chloroplasts.

The nucleotide sequences of the ribosomal protein genes rps18, rps19, rpl2, rpl33, and partial sequence of rpl22 from cyanelles, the photosynthetic organelles of the protist Cyanophora paradoxa, have been determined. These genes form two clusters oriented in opposite and divergent directions. One cluster contains the rpl33 and rps18 genes; the other contains the rpl2, rps19, and rpl22 genes, in that order. Phylogenetic trees were constructed from both the DNA sequences and the deduced protein sequences of cyanelles, Euglena gracilis and land plant chloroplasts, and Escherichia coli, using parsimony or maximum likelihood methods. In addition, a phylogenetic tree was built from a distance matrix comparing the number of nucleotide substitutions per site. The phylogeny inferred from all these methods suggests that cyanelles fall within the chloroplast line of evolution and that the evolutionary distances between cyanelles and land plant chloroplasts are shorter than between E. gracilis chloroplasts and land plant chloroplasts.