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Eukaryotic Cell, June 2005, p. 1137-1146, Vol. 4, No. 6
1535-9778/05/$08.00+0     doi:10.1128/EC.4.6.1137-1146.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Unique Mitochondrial Genome Structure in Diplonemids, the Sister Group of Kinetoplastids

William Marande,1 Julius Lukes,2 and Gertraud Burger1,3*

Université de Montréal, Robert-Cedergren Centre for Bioinformatics and Genomics, Department of Biochemistry, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec H3T 1J4, Canada,1 Institute of Parasitology, Czech Academy of Sciences and Faculty of Biology, University of South Bohemia, 37005 Ceské Budejovice, Czech Republic,2 Program in Evolutionary Biology, Canadian Institute for Advanced Research, Toronto, Ontario, Canada3

Received 27 January 2005/ Accepted 19 April 2005

Kinetoplastid flagellates are characterized by uniquely massed mitochondrial DNAs (mtDNAs), the kinetoplasts. Kinetoplastids of the trypanosomatid group possess two types of mtDNA molecules: maxicircles bearing protein and mitoribosomal genes and minicircles specifying guide RNAs, which mediate uridine insertion/deletion RNA editing. These circles are interlocked with one another to form dense networks. Whether these peculiar mtDNA features are restricted to kinetoplastids or prevail throughout Euglenozoa (euglenids, diplonemids, and kinetoplastids) is unknown. Here, we describe the mitochondrial genome and the mitochondrial ultrastructure of Diplonema papillatum, a member of the diplonemid flagellates, the sister group of kinetoplastids. Fluorescence and electron microscopy show a single mitochondrion per cell with an ultrastructure atypical for Euglenozoa. In addition, DNA is evenly distributed throughout the organelle rather than compacted. Molecular and electron microscopy studies distinguish numerous 6- and 7-kbp-sized mitochondrial chromosomes of monomeric circular topology and relaxed conformation in vivo. Remarkably, the cox1 gene (and probably other mitochondrial genes) is fragmented, with separate gene pieces encoded on different chromosomes. Generation of the contiguous cox1 mRNA requires trans-splicing, the precise mechanism of which remains to be determined. Taken together, the mitochondrial gene/genome structure of Diplonema is not only different from that of kinetoplastids but unique among eukaryotes as a whole.

* Corresponding author. Mailing address: Université de Montréal, Robert-Cedergren Centre for Bioinformatics and Genomics, Department of Biochemistry, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec H3T 1J4, Canada. Phone: (514) 343-7936. Fax: (514) 343-2210. E-mail: gertraud.burger{at}umontreal.ca.

Eukaryotic Cell, June 2005, p. 1137-1146, Vol. 4, No. 6
1535-9778/05/$08.00+0     doi:10.1128/EC.4.6.1137-1146.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Lukes, J., Leander, B. S., Keeling, P. J. (2009). Colloquium Papers: Cascades of convergent evolution: The corresponding evolutionary histories of euglenozoans and dinoflagellates. Proc. Natl. Acad. Sci. USA 106: 9963-9970 [Abstract] [Full Text]  
  • Shao, R., Kirkness, E. F., Barker, S. C. (2009). The single mitochondrial chromosome typical of animals has evolved into 18 minichromosomes in the human body louse, Pediculus humanus. Genome Res 19: 904-912 [Abstract] [Full Text]  
  • Marande, W., Burger, G. (2007). Mitochondrial DNA as a Genomic Jigsaw Puzzle. Science 318: 415-415 [Abstract] [Full Text]  


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