Plasmid Loss in Agaricus bitorquis without Alterations in Homologous Mitochondrial Sequences

Robison, M. M., and Horgen, P. A. (1993). Plasmid loss in Agaricus bitorquis without alterations in homologous mitochondrial sequences. Experimental Mycology , 18, 82-86. An isolate of the basidiomycete Agaricus bitorquis , a common edible lawn mushroom, contains two linear mitochondrial plasmids. With the intent of creating a plasmidless (or "cured") version of this isolate for future studies on a plasmid-homologous mitochondrial sequence, mycelium was grown in the presence of 50 μg/ml ethidium bromide. Regenerates were recovered that had lost only the larger plasmid or both plasmids. No obvious effects on mycelial or mushroom phenotype, associated with plasmid loss, were observed. Restriction fragment length polymorphism analysis of mitochondrial DNAs from 23 regenerates indicated that no apparent deletions or rearrangements of the mitochondrial DNA, particularly the plasmid-homologous mitochondrial sequence, occurred as a result of plasmid loss or ethidium bromide treatment.