Browse by author
Lookup NU author(s): Dr Christophe Noel
Full text for this publication is not currently held within this repository. Alternative links are provided below where available.
Class II fumarase sequences were obtained by polymerase chain reaction from five trichomonad species. All residues known to be highly conserved in this enzyme were present. Nuclear run-on assays showed that one of the two genes identified in Tritrichomonas foetus was expressed, whereas no fumarase transcripts were detected in the related species Trichomonas vaginalis. These findings corroborate previous biochemical data. Fumarase genes were also expressed in Monocercomonas sp. and Tetratrichomonas gallinarum but not in Pentatrichomonas hominis, Trichomonas gallinae, Trichomonas tenax, and Trichomitus batrachorum under the culture conditions used. Molecular trees inferred by likelihood methods reveal that trichomonad sequences have no affinity to described class II fumarase genes from other eukaryotes. The absence of functional mitochondria in protists such as trichomonads suggests that they diverged from other eukaryotes prior to the alpha-proteobacterial symbiosis that led to mitochondria. Furthermore, they are basal to other eukaryotes in rRNA analyses. However, support for the early-branching status of trichomonads and other amitochondriate protists based on phylogenetic analyses of multiple data sets has been equivocal. Although the presence of hydrogenosomes suggests that trichomonads once had mitochondria, their class II iron-independent fumarase sequences differ markedly from those of other mitochondriate eukaryotes. All of the class II fumarase genes described from other eukaryotes are of apparent alpha-proteobacterial origin and hence a marker of mitochondrial evolution. In contrast, the class II fumarase from trichomonads emerges among other eubacterial homologs. This is intriguing evidence for an independent acquisition of these genes in trichomonads apart from the mitochondrial endosymbiosis event that gave rise to the form present in other eukaryotes. The ancestral trichomonad class II fumarase may represent a prokaryotic form that was replaced in other eukaryotes after the divergence of trichomonads with the movement of endosymbiont genes into the nucleus. Alternatively, it may have been acquired via a separate endosymbiotic event or lateral gene transfer.
Author(s): Noel C; Gerbod D; Edgcomb VP; Vanacova S; Wintjens R; Tachezy J; Sogin ML; Viscogliosi E
Publication type: Article
Publication status: Published
Journal: Molecular Biology and Evolution
Year: 2001
Volume: 18
Issue: 8
Pages: 1574-84
ISSN (print): 0737-4038
ISSN (electronic): 1537-1719
Publisher: Oxford University Press
URL: http://dx.doi.org/10.1093/oxfordjournals.molbev.a003944
DOI: 10.1093/oxfordjournals.molbev.a003944
Notes: 0737-4038 Journal Article
Altmetrics provided by Altmetric
