Mosaic Genes and Unidentified Reading Frames That Have Homology with Human Mitochondrial Sequences Are Found in the Mitochondrial Genome of Aspergillus nidulans

Abstract

The ascomycete fungus Aspergillus nidulans is an obligate aerobe in which a good nuclear genetic system and the basis of a mitochondrial one have been developed (Waring and Scazzocchio 1981). We are now determining the complete DNA sequence of the mitochondrial genome of this organism and have sequenced random fragments using the M13 cloning-sequencing system (Sanger et al. 1980). We have also subcloned interesting regions as 1- to 4-kb fragments and then sequenced them in a similar way. We had previously located five genes on the physical map by homology with yeast petite mutant DNAs (Macino et al. 1980), and the sequencing of these genes has uncovered many interesting features of the genome, including two mosaic genes with potential intron-coded splicing functions and two open reading frames that also occur in the mitochondrial genomes of man and other mammals. The mitochondrial genome of A. nidulans is quite different from those of yeast and man, and a comparison of the three will be important to our understanding of how mitochondrial genomes function.

GENERAL STRUCTURE OF THE MITOCHONDRIAL GENOME OF A. NIDULANS
Figure 1 is a physical map summarizing our knowledge about this genome thus far. We can already say that the information content of the mtDNA of A. nidulans differs from that of Saccharomyces cerevisiae. We find two unidentified reading frames that have not yet been found in S. cerevisiae despite extensive sequencing, and it is known that the oli1 gene of yeast mitochondria is located in the nuclear genome in...