Evidence That Plant-Like Genes in Chlamydia Species Reflect an Ancestral Relationship between Chlamydiaceae, Cyanobacteria, and the Chloroplast

  1. Fiona S.L. Brinkman1,2,3,12,13,
  2. Jeffrey L. Blanchard4,5,
  3. Artem Cherkasov3,
  4. Yossef Av-Gay6,
  5. Robert C. Brunham7,
  6. Rachel C. Fernandez2,
  7. B. Brett Finlay2,
  8. Sarah P. Otto8,
  9. B.F. Francis Ouellette9,
  10. Patrick J. Keeling10,
  11. Ann M. Rose3,
  12. Robert E.W. Hancock2, and
  13. Steven J.M. Jones11
  1. 1Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6; 2Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3; 3Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada, V6H 3N1; 4Promega Corporation, Madison, Wisconsin 53711, USA; 5National Center for Genome Resources, Santa Fe, New Mexico 87505, USA; 6Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada, V5Z 4E3; 7University of British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada, V5Z 4R4; 8Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4; 9Centre for Molecular Medicine and Therapeutics, Vancouver, British Columbia, Canada, V5Z 4H4; 10Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4; and 11Genome Sequence Centre, British Columbia Cancer Agency, Vancouver, British Columbia, Canada, V5Z 4E6

Abstract

An unusually high proportion of proteins encoded inChlamydia genomes are most similar to plant proteins, leading to proposals that a Chlamydia ancestor obtained genes from a plant or plant-like host organism by horizontal gene transfer. However, during an analysis of bacterial–eukaryotic protein similarities, we found that the vast majority of plant-like sequences in Chlamydia are most similar to plant proteins that are targeted to the chloroplast, an organelle derived from a cyanobacterium. We present further evidence suggesting that plant-like genes in Chlamydia, and other Chlamydiaceae, are likely a reflection of an unappreciated evolutionary relationship between the Chlamydiaceae and the cyanobacteria-chloroplast lineage. Further analyses of bacterial and eukaryotic genomes indicates the importance of evaluating organellar ancestry of eukaryotic proteins when identifying bacteria-eukaryote homologs or horizontal gene transfer and supports the proposal that Chlamydiaceae, which are obligate intracellular bacterial pathogens of animals, are not likely exchanging DNA with their hosts.

[Supplementary Material is available online at http://www.genome.org and athttp://www.pathogenomics.bc.ca/BAE-watch.html.]

Footnotes

  • 12 Corresponding author.

  • 13 Present address: Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6.

  • E-MAIL brinkman{at}sfu.ca; FAX (604) 291-5583.

  • Article and publication are at http://www.genome.org/cgi/doi/10.1101/gr.341802. Article published online before print in July 2002.

    • Received April 9, 2002.
    • Accepted May 23, 2002.
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