Plasmid DNA in Mycelial Fungi

The Cryphonectria parasitica mitochondrial rns gene: Plasmid-like elements, introns and homing endonucleases

“…This proposal gathers support not only from a report indicating that ethidium bromide induces mtDNA deletions in N. crassa (Niagro and Mishra, 1989), but also from the well-documented observation that the exposure of cells of the budding yeast Saccharomyces cereviseae to DNA intercalating agents, particularly ethidium bromide, results in massive mtDNA rearrangements and the accumulation of plasmid-like excision sequences, the so-called rho À repetitive DNA elements De Zamaroczy et al, 1983). Mitochondrial plasmids and plasmid like elements are known to be associated with specific phenotypes in some filamentous fungi (reviewed by Kempken, 1995). We have concluded that the plME of C. parasitica does not cause a discrete phenotype because it is not transmitted in sexual crosses even though the hypovirulence phenotype is maternally inherited, as expected of a trait that is determined by a mutant form of mtDNA.…”

“…Circular mtDNA-derived plMEs that exist in multimeric forms also have been found to be associated with a degenerative disease in the plant-pathogenic fungus Ophiostoma novo-ulmi (Charter et al, 1993;Abu-Amero et al, 1995). In the filamentous fungi, the mechanisms involved in the initial formation of mitochondrial plMEs, their amplification, mode of inheritance and physiological effects are still poorly understood (reviewed in Griffiths, 1992Griffiths, , 1995Griffiths, , 1996Griffiths et al, 1995;Kempken, 1995;Hausner et al, 2006a). However, there are instances where plMEs can have important functions in mtDNA maintenance; for example, in some yeasts (e.g.…”

Relocation of a cytoplasmic yeast linear plasmid to the nucleus is associated with circularization via nonhomologous recombination involving inverted terminal repeats

“…Similarly, one of the TP-free ITR ends of pCLU1 may have a transposon-like ability to insert into non-speci®c sites within itself. A number of eukaryotic and prokaryotic linear plasmids, bacteriophages and viruses seem to be evolutionarily linked and may share the ability to transpose (Sakaguchi 1990;Chan et al 1991;Kempken 1995). The possible integration of pCLU1-ITR end(s) into the host chromosomes remains to be clari®ed.…”

“…Adenovirus DNAs (Frolova and Zalmanzon 1984;Salas 1991), the maize plasmids S1 and S2 (Schardl et al 1985), and mitochondrial plasmids in fungi, such as kalilo in Neurospora (Kempken 1995;Chan et al 1991) integrate into the host genomes via their ITR structures. Similarly, one of the TP-free ITR ends of pCLU1 may have a transposon-like ability to insert into non-speci®c sites within itself.…”

The ectomycorrhizal basidiomycete Hebeloma circinans harbors a linear plasmid encoding a DNA- and RNA polymerase.

“…They encode virallike DNA-and/or RNA-polymerases only, making them independent from their hosts in terms of replication and transcription. Comparative sequence analyses have revealed phylogenetic relations among several linear elements, such as adenoviruses, phages with linear genomes, cytoplasmic killer plasmids of yeasts, and the mitochondria) linear plasmids of filamentous fungi (Griffiths, 1995;Kempken, 1995;Meinhardt et SLI., 1990;Schrunder and Meinhardt, 1995). Linear plasmids have been very rarely described in basidiomycetes and, up to now, for only one element, pEM of Agaricus bitorquis (Robison et al, 1991), is sequence data available.…”