title: Horizontal gene transfer of chlamydial-like tRNA genes into early vascular plant mitochondria.
abstract: Mitochondrial genomes of lycophytes are surprisingly diverse, including strikingly different transfer RNA (tRNA) gene complements: No mitochondrial tRNA genes are present in the spikemoss Selaginella moellendorffii, whereas 26 tRNAs are encoded in the chondrome of the clubmoss Huperzia squarrosa. Reinvestigating the latter we found that trnL(gag) and trnS(gga) had never before been identified in any other land plant mitochondrial DNA. Sensitive sequence comparisons showed these two tRNAs as well as trnN(guu) and trnS(gcu) to be very similar to their respective counterparts in chlamydial bacteria. We identified homologs of these chlamydial-type tRNAs also in other lycophyte, fern, and gymnosperm DNAs, suggesting horizontal gene transfer (HGT) into mitochondria in the early vascular plant stem lineages. These findings extend plant mitochondrial HGT to affect individual tRNA genes, to include bacterial donors, and suggest that Chlamydiae on top of their recently proposed key role in primary chloroplast establishment may also have participated in early tracheophyte genome evolution.
authors.affiliation: Abteilung Molekulare Evolution, Institut für Zelluläre und Molekulare Botanik, Universität Bonn, Bonn, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Knie
authors.affiliation: Abteilung Molekulare Evolution, Institut für Zelluläre und Molekulare Botanik, Universität Bonn, Bonn, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Polsakiewicz
authors.affiliation: Abteilung Molekulare Evolution, Institut für Zelluläre und Molekulare Botanik, Universität Bonn, Bonn, Germany volker.knoop@uni-bonn.de.
authors.forename: Volker
authors.initials: V
authors.lastname: Knoop
mesh_terms: D002695:Chlamydiales / Q000235:genetics*; D002736:Chloroplasts / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D050259:Genes, Mitochondrial; D032501:Huperzia / Q000235:genetics*; D010802:Phylogeny; D010944:Plants / Q000145:classification / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D012343:RNA, Transfer
keywords: Chlamydiae; Class II tRNAs; gymnosperms; horizontal gene transfer (HGT); lycophytes; mitochondrial tRNA genes; monilophytes