Non-mitochondrial complex I proteins in a hydrogenosomal oxidoreductase complex

Area of Science:

• Cell biology
• Evolutionary biology
• Microbiology

Background:

• Trichomonas vaginalis possesses hydrogenosomes, not mitochondria, for pyruvate metabolism.
• Hydrogenosomes feature unique pathways like pyruvate:ferredoxin oxidoreductase (PFOR) and [Fe]-hydrogenase, differing from mitochondrial processes.
• The endosymbiotic origin of hydrogenosomes remains unclear due to their lack of a genome.

Purpose of the Study:

• To investigate the evolutionary origin of Trichomonas vaginalis hydrogenosomes.
• To characterize a novel NADH dehydrogenase module within the hydrogenosomal oxidoreductase complex.
• To compare the phylogenetic origins of hydrogenosomal and mitochondrial proteins.

Main Methods:

• Phylogenetic analyses of hydrogenosomal complex I-like proteins (Ndh51 and Ndh24).
• Characterization of a novel NADH dehydrogenase module coupled to the hydrogenosomal fermentative pathway.
• Comparison of protein origins between hydrogenosomes and mitochondria.

Main Results:

• A novel NADH dehydrogenase module, functioning independently of quinones, was identified in hydrogenosomes.
• Phylogenetic analyses showed that Ndh51 and Ndh24 proteins do not share a common origin with their mitochondrial counterparts.
• These findings challenge the notion of a direct vertical inheritance from the proto-mitochondrial endosymbiont.

Conclusions:

• Trichomonad hydrogenosomes likely did not originate vertically from the proto-mitochondrial endosymbiont.
• The evolutionary history of hydrogenosomes is distinct from that of mitochondria.
• This study provides new insights into the diverse evolutionary trajectories of eukaryotic organelles.