DNA sequence, structure, and phylogenetic relationship of the small subunit rRNA coding region of mitochondrial DNA fromPodospora anserina

Abstract

DNA sequence analysis and the localization of the 5' and 3' termini by S1 mapping have shown that the mitochondrial (mt) small subunit rRNA coding region from Podospora anserina is 1980 bp in length. The analogous coding region for mt rRNA is 1962 bp in maize, 1686 bp in Saccharomyces cerevisiae, and 956 bp in mammals, whereas its counterpart in Escherichia coli is 1542 bp. The P. anserina mt 16S-like rRNA is 400 bases longer than that from E. coli, but can be folded into a similar secondary structure. The additional bases appear to be clustered at specific locations, including extensions at the 5' and 3' termini. Comparison with secondary structure diagrams of 16S-like RNAs from several organisms allowed us to specify highly conserved and variable regions of this gene. Phylogenetic tree construction indicated that this gene is grouped with other mitochondrial genes, but most closely, as expected, with the fungal mitochondrial genes.