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Widespread distribution of low-copy-number variants of mitochondrial plasmid pEM in the genus Agaricus

M M Robison1, P A Horgen

  • 1Department of Botany, University of Toronto at Mississauga, Mississauga, Ontario, L5L 1C6, Canada.

Fungal Genetics and Biology : FG & B
|March 11, 1999
PubMed

Insights

Linear mitochondrial plasmid pEM is widespread in Agaricus fungi, detected via PCR. Sequence analysis suggests recent plasmid acquisition, challenging previous assumptions of its rarity.

Area of Science:

  • Mycology
  • Molecular Biology
  • Genetics

Background:

  • The linear mitochondrial plasmid pEM was previously thought to be rare in Agaricus species.
  • Detection relied on gel electrophoresis and Southern hybridization, potentially underestimating its prevalence.

Purpose of the Study:

  • To investigate the actual incidence of pEM-like sequences in Agaricus fungi.
  • To characterize the genetic features and evolutionary history of these sequences.

Main Methods:

  • Polymerase Chain Reaction (PCR) amplification of pEM RNA polymerase gene and adjacent regions.
  • DNA sequencing and comparative analysis of amplified products.
  • Phylogenetic analysis using parsimony methods.

Main Results:

  • PCR detected pEM-like sequences in all but one examined Agaricus species.
  • Sequence data supported a plasmid origin, not mitochondrial.
  • Low sequence variation with mostly silent or conservative amino acid changes.
  • Phylogenetic analysis of plasmid sequences did not align with host species phylogeny.

Conclusions:

  • The linear mitochondrial plasmid pEM is more common in Agaricus than previously believed.
  • Recent acquisition of the plasmid by the Agaricus lineage is the most plausible explanation for the observed data.
  • This finding necessitates a re-evaluation of plasmid-host interactions and evolution in fungi.

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