DISTRIBUTION OF PLASMIDS AND A PLASMID-LIKE MITOCHONDRIAL SEQUENCE INTHE GENUS AGARICUS

Representatives of 21 species of the basidiomycete Agaricus were exami ned for the presence of the linear mitochondrial plasmid, pEM, and mit ochondrial sequences that hybridize to the pEM RNA polymerase gene. pE M-like plasmids were detected in only two species although other types of plasmids were detected in eight species. pEM RNA polymerase-like s equences were detected in the mitochondrial DNA of 20 species. A commo n sequence ancestor to the pEM plasmid and to the mitochondrial RNA po lymerase-like sequences probably existed in the Agaricus mitochondrial ancestor prior to speciation of the genus.