Parabasalian flagellates are ancient eukaryotes

摘要

Discrepancies between eukaryotic phylogenetic trees based on different gene sequences have led to the suggestion that the deepest branches of each gene tree could simply be artefacts of rapid evolution rather than indicators of an ancient divergence. But if an insertion or deletion occurred in a gene sequence very early in eukaryotic evolution, the oldest eukaryotic lineages should be recognizable by their resemblance to prokaryotes lacking this character. Here we investigate the structure of the gene encoding enolase, an enzyme of the glycolytic pathway, and find that the gene from parabasalian flagellates lacks two deletions present in other eukaryotic enolases, indicating that Parabasalia could be the most ancient eukaryotes examined so far.