Interaction between mitochondria derived from incompatible black Aspergillus isolates.

As black Aspergillus isolates are highly heterokaryon-incompatible mitochondrial transmissions were performed by protoplast fusion. Donor strains with oligomycin-resistant mitochondria and sensitive recipient partners of various A. japonicus isolates were applied and the progeny were selected for oligomycin resistance and for recipient nuclear phenotype. These strains basically inherited the mitochondrial DNA of the donor strain, which might remain unchanged (substituted progeny) or might be modified by specific sequences of the recipient mtDNAs (recombinant progeny). Different mobile elements characteristic of the recipient parents were exclusively responsible for the development of the feature of recombinant mtDNAs. Substituted progeny were either stable wild-type-like strains as a result of compatible co-operation between donor mitochondria and recipient nuclei, or aconidial strains with a reduced fitness, exhibiting a certain instability. The latter type was probably due to the less compatible communication between nuclear and extrachromosomal genetic systems originating from different parents. These progeny were able to undergo some developmental (segregation) processes during subsequent cultivation, resulting in a stable, wild-type phenotype which possessed a new type of mtDNA resembling that of the acceptor parents.