Strains of the Aspergillus niger aggregate can be divided to three main groups based on their HaellI-Bglll digested mtDNA patterns. The first and second groups correspond to A. niger and A. tubingensis species respectively, while the third type is represented only by some wild-type isolates derived from Brazil (mtDNA types 1, 2 and 3 correspond to rDNA groups I, II, and III, respectively). The mtDNA types I and 2 consist of several subgroups (labelled la - le, and 2a - 2f, respectively) . Successful mitochondrial transfers were performed by protoplast fusion. Recombination of mtDNA occurred among strains representing different mtDNA groups or subgroups. All these strains showed full incompatibility in respect of nuclear complementation. Transfer experiments were carried out under selection pressure using a mitochondrial oligomycin resistant (oliR) mutant as a donor, which exhibits type la mtDNA and type I rDNA. Mitochondrial oliR progenies could be recovered following protoplast fusion in the presence of oligomycin by selecting for the nuclear phenotypes of the oliS recipient strains. The transfers were successful in all possible combinations. Within the group of strains belonging to mtDNA type I the transfers resulted in a single type of recombinant RFLP profile in each subgroup. The recombination events were more complex when the transfer of oliR occurred between strains representing different species. A great variety of recombined RFLP profiles of the partners appeared. In mtDNA transfers la 2b and la 2d, resistant clones harbouring possibly unchanged donor mitochondria with the nuclear background of the recipient strain were also recovered in addition to the recombinant types.
Full conference title:
3rd EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 3rd (1996)