Maternal inheritance of chloramphenicol tolerance in Ophiostoma ulmi

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.

De-novo generation of mitochondrial DNA plasmids following cytoplasmic transmission of a degenerative disease in Ophiostoma novo-ulmi

A mitochondrial DNA plasmid was detected in an isolate of Ophiostoma novo-ulmi with a degenerative disease. The DNA plasmid was shown to be derived from the mitochondrial DNA and to map to a region corresponding to the large ribosomal RNA coding region. The DNA plasmid was not transmitted into sexual (ascospore) progeny, irrespective of whether the diseased isolate acted as the female or male parent. Transmission of the disease to healthy, plasmid-free, "recipient" isolates by hyphal anastomosis was not accompanied by transfer of mitochondrial DNA or DNA plasmid from the diseased "donor" isolate, but resulted in de-novo generation of different plasmids, derived from the recipient's mitochondrial DNA.