Phylogenetic tree derived from bacterial, cytosol and organelle 5S rRNA sequences

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Abstract
A phylogenetic tree was constructed by computer analysis of 47 completely determined 5S rRNA sequences. The wheat mitochondrial sequence is significantly more related to pro-karyotic than to eukaryotic sequences, and its affinity to that of the thermophilic Gram-negative bacterium Thermus aquaticus is comparable to the affinity between Anacystis nidulans and chloroplastic sequences. This strongly supports the idea of an endosymbiotic origin of plant mitochondria. A comparison of the plant cytosol and chloroplast sub-trees suggests a similar rate of nucleotide substitution in nuclear genes and chloroplastic genes. Other features of the tree are a common precursor of protozoa and metazoa, which appears to be more related to the fungal than to the plant proto-sequence, and an early divergence of the archebacterial sequence (Halobacterium cutirubrum) from the prokaryotic branch.