Amplification of a mitochondrial DNA sequence in the cytoplasmically inherited 'ragged' mutant of Aspergillus amstelodami.

A comparison has been made between mtDNA of the cytoplasmically inherited 'ragged' mutant of Aspergillus amstelodami and that of the wild-type strain. Ragged mitochondria contain both the wild-type mitochondrial genome and several large DNA molecules which are not cleaved by the restriction endonucleases BamHI, HaeIII, HhaI, HindII, HindIII, PstI and MboI, but are converted by either EcoRI or HpaII into a single 820-840 base-pair fragment. Restriction analysis and molecular hybridization data indicate that this fragment contains sequences of wild-type mtDNA located within a 1200-base-pair segment of the 40,500-base-pair genome, for which a basic restriction map has been deduced. It is concluded that in the ragged mutant a small segment of wild-type mtDNA has been amplified as tandem repeats, which is reminiscent of the Rho- petite phenotype of yeast. The results are discussed in relation to the phenomenon of senescence in Podospora anserina.