Current Genetics

, Volume 57, Issue 4, pp 225–232 | Cite as

Gene fragmentation: a key to mitochondrial genome evolution in Euglenozoa?

  • Pavel Flegontov
  • Michael W. Gray
  • Gertraud Burger
  • Julius Lukeš


Phylum Euglenozoa comprises three groups of eukaryotic microbes (kinetoplastids, diplonemids, and euglenids), the mitochondrial (mt) genomes of which exhibit radically different modes of organization and expression. Gene fragmentation is a striking feature of both euglenid and diplonemid mtDNAs. To rationalize the emergence of these highly divergent mtDNA types and the existence of insertion/deletion RNA editing (in kinetoplastids) and trans-splicing (in diplonemids), we propose that in the mitochondrion of the common evolutionary ancestor of Euglenozoa, small expressed gene fragments promoted a rampant neutral evolutionary pathway. Interactions between small antisense transcripts of these gene fragments and full-length transcripts, assisted by RNA-processing enzymes, permitted the emergence of RNA editing and/or trans-splicing activities, allowing the system to tolerate indel mutations and further gene fragmentation, respectively, and leading to accumulation of additional mutations. In this way, dramatically different mitochondrial genome structures and RNA-processing machineries were able to evolve. The paradigm of constructive neutral evolution acting on the widely different mitochondrial genetic systems in Euglenozoa posits the accretion of initially neutral molecular interactions by genetic drift, leading inevitably to the observed ‘irremediable complexity’.


Euglena Diplonema Mitochondrial genome RNA editing Constructive neutral evolution 


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Pavel Flegontov
    • 1
  • Michael W. Gray
    • 2
  • Gertraud Burger
    • 3
  • Julius Lukeš
    • 1
  1. 1.Biology Centre, Institute of Parasitology, Czech Academy of Sciences, and Faculty of SciencesUniversity of South BohemiaČeské BudĕjoviceCzech Republic
  2. 2.Centre for Comparative Genomics and Evolutionary Bioinformatics, and Department of Biochemistry and Molecular BiologyDalhousie UniversityHalifaxCanada
  3. 3.Robert-Cedergren Center in Bioinformatics and Genomics, and Department of BiochemistryUniversité de MontréalMontrealCanada

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