Intron mobility results in rearrangement in mitochondrial DNAs of heterokaryon incompatible Aspergillus japonicus strains after protoplast fusion.

Mitochondrial transmission was carried out under selective conditions between incompatible Aspergillus japonicus strains always using an oligomycin-resistant mitochondrial donor and selecting for recipient nuclei and oligomycin-resistant mitochondria. All attempted intraspecific mitochondrial transmissions were successful, but the transmission between closely related A. japonicus and A. aculeatus failed. Under selection pressure, resistant progeny harbor the mitochondrial DNA (mtDNA) of the donor strain, which may remain unchanged or may be modified by the introns of the recipient mitochondrial genome. Detailed analysis of a certain strain harboring rearranged mtDNA suggests that the mtDNA profiles of recombinant-like progeny are strongly influenced by the characteristics and mobility of introns of both parental mtDNAs. Both intron loss and intron acquisition play a role in the rearrangement of mtDNA. In certain parental combinations, a particular intron was lost very frequently.