Recombination of mitochondrial DNAs following transmission of mitochondria among incompatible strains of black Aspergilli |
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Authors: | F Kevei B Tóth A Coenen Z Hamari J Varga and J H Croft |
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Institution: | (1) Department of Microbiology, Attila József University, P.O. Box 533, H-6701 Szeged, Hungary, HU;(2) Department of Genetics, Agricultural University, Wageningen, Dreijenlaan 2, 6703 HA, The Netherlands, NL;(3) School of Biological Sciences, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, United Kingdom, GB |
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Abstract: | Successful intra- and interspecific mitochondrial transfers were performed by polyethylene glycol (PEG)-induced protoplast
fusion among incompatible strains belonging to the Aspergillus niger species aggregate. The mitochondrial DNAs (mtDNAs) of the strains examined were of three main types based on their restriction
fragment length polymorphism (RFLP) profiles. mtDNA types 1 and 2 correspond to A. niger and A. tubingensis species, respectively, while type 3 is represented by some Brazilian wild-type isolates (possibly a distinct species or subspecies).
mtDNA types 1 and 2 could be further divided into several subgroups (1a–1e and 2a–2f ). All these strains, representing different
RFLP groups or subgroups, were fully incompatible with respect to nuclear complementation. The transfer experiments were carried
out under selection pressure, using a mitochondrial oligomycin-resistant mutant of mtDNA type 1a as donor. Following fusion
mitochondrial oligomycin-resistant progenies were recovered in the presence of oligomycin by selecting for the nuclear phenotypes
of the oligomycin-sensitive recipient strains. All attempted transfers were successful, and resulted in different varieties
of resistant recombinant mitochondrial progenies at various frequencies. Within the group of strains of mtDNA type 1, the
transfer of oligomycin-resistant mitochondria resulted in the appearance of a single recombinant type of RFLP profile in each
case. The recombination events were more complex when the transfer of oligomycin resistance occurred between strains representing
different species (mtDNA groups 1a→2 and 1a→3). A great variety of recombinant mtDNA RFLP profiles appeared. Explanation for
this phenomenon are discussed on the basis of preliminary physical mapping data.
Received: 16 July 1996 / Accepted: 2 December 1996 |
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Keywords: | Mitochondrial transfer mtDNA recombination Incompatibility Aspergillus niger |
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