ABSTRACT
The Agrocybe aegerita mitochondrial genome contains a truncated family B DNA polymerase gene (Aa-polB P1) whose nucleotide sequence is 86% identical to the previously described and potentially functional Aa-polB gene. A tRNAMetgene occurs at the 3′ end of the Aa-polB P1 gene. TheAa-polB P1 gene could result from reverse transcription of an Aa-polB mRNA primed by a tRNAMet followed by the integration of the cDNA after recombination at the mitochondrial tRNA locus. Two naturally occurring alleles of Aa-polB P1carry one or two copies of the disrupted sequence. In strains with two copies of Aa-polB P1, these copies are inverted relative to one another and separated by a short sequence carrying the tRNAMet gene. Both A. aegerita mitochondrial family B DNA polymerases were found to be related to other family B DNA polymerases (36 to 53% amino acid similarity), including the three enzymes of the archaebacterium Sulfolobus solfataricus. If mitochondria originated from a fusion between aClostridium-like eubacterium and aSulfolobus-like archaebacterium, then the A. aegerita family B DNA polymerase genes could be remnants of the archaebacterial genes.
Wide Distribution of Mitochondrial Genome Rearrangements in Wild Strains of the Cultivated Basidiomycete Agrocybe aegerita.
