The 32 S RNA of Neurospora crassa mitochondria is not a precursor of the mitochondrial ribosomal RNAs

Mitochondrial DNA from Podospora anserina : IV. The large ribosomal RNA gene contains two long intervening sequences

We have examined the structure of the rRNA genes from the mitochondrial genome of Podospora anserina. Using R-loop analysis, nuclease protection experiments, and Southern blot hybridization analysis we have observed two intervening sequences (IVS) in the large rRNA gene, and none in the small rRNA gene. the IVS sequences are 1.65 kbp and 2.73 kbp long, and the larger of the two is in the position of the conserved IVS found in the mitochondrial genomes of other fungi. We have detected precursor transcripts for the large rRNA, and these data support the observation of two IVS in this gene. We also note that the large and small rRNA genes are separated by approximately 6 kbp of DNA.

Organization of rRNA structural genes in the archaebacterium Thermoplasma acidophilum

In the archaebacterium Thermoplasma acidophilum, each of the structural genes for 5S, 16S and 23S rRNA occur once per genome. In contrast to those of eubacteria and eukaryotes, they appear unlinked. The distance between the 16S and the 23S rDNA is at least 7.5 Kb, that between 23S and 5S rDNA at least 6 Kb and that between 16S and 5S rDNA at least 1.5 Kb. No linkage between those genes has been found by the analysis of recombinant plasmids carrying Bam HI and Hind III rDNA fragments as by hybridizing those plasmids to fragments of Thermoplasma DNA generated by 6 individual restriction endonucleases, recognizing hexanucleotide sequences.