title: Evidence that plant-like genes in Chlamydia species reflect an ancestral relationship between Chlamydiaceae, cyanobacteria, and the chloroplast.
abstract: An unusually high proportion of proteins encoded in Chlamydia 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.
authors.affiliation: Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6. brinkman@sfu.ca
authors.forename: Fiona S L
authors.initials: FS
authors.lastname: Brinkman
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Blanchard
authors.forename: Artem
authors.initials: A
authors.lastname: Cherkasov
authors.forename: Yossef
authors.initials: Y
authors.lastname: Av-Gay
authors.forename: Robert C
authors.initials: RC
authors.lastname: Brunham
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Fernandez
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Otto
authors.forename: B F Francis
authors.initials: BF
authors.lastname: Ouellette
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Keeling
authors.forename: Ann M
authors.initials: AM
authors.lastname: Rose
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
authors.forename: Steven J M
authors.initials: SJ
authors.lastname: Jones
authors.forename: Hans
authors.initials: H
authors.lastname: Greberg
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001482:Base Composition / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics; D002689:Chlamydia / Q000235:genetics*; D002693:Chlamydiaceae / Q000235:genetics*; D002736:Chloroplasts / Q000235:genetics*; D019295:Computational Biology / Q000379:methods; D000458:Cyanobacteria / Q000235:genetics*; D030541:Databases, Genetic; D030562:Databases, Protein; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D005798:Genes, Bacterial / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D016680:Genome, Bacterial; D006801:Humans; D008928:Mitochondria / Q000235:genetics; D010802:Phylogeny; D012281:Rickettsia / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D029742:Caenorhabditis elegans Proteins; D029721:Drosophila Proteins; D029701:Saccharomyces cerevisiae Proteins