High frequency transfer of species specific mitochondrial DNA sequences between members of the aspergillaceae.

The mitochondrial genome of Aspergillus nidulans var. echinulatus is approximately 20% larger than that of the closely related species Aspergillus nidulans (Eidam) Winter. Restriction enzyme mapping and electron microscopy has revealed that the size difference is due to the presence of six inserted sequences in the former. With the exception of a small number of species specific restriction sites and the six insertions/deletions, the two mitochondrial genomes appear identical. Protoplast fusion between the two species followed by selection of extranuclear drug resistance markers resulted in the isolation of recombinant mitochondrial genomes in an A. nid. var. echinulatus background. Restriction maps of the hybrid genomes indicated that three of the additional sequences found in A. nid. var. echinulatus could be transferred to the A. nidulans nuclear background without loss or detectable alteration. The nature of the additional mitochondrial DNA and high frequency transfer of certain species specific sequences is discussed with reference to studies in yeast and Neurospora crassa.