Protein coding gene trees in ciliates: comparison with rRNA-based phylogenies.

Area of Science:

• * Molecular Phylogenetics
• * Protistology
• * Evolutionary Biology

Background:

• * The phylum Ciliophora is a diverse group of eukaryotic microorganisms.
• * Understanding the evolutionary relationships within ciliates is crucial for their classification and study.
• * Gene sequence data offers powerful tools for phylogenetic reconstruction.

Purpose of the Study:

• * To reexamine the phylogeny of ciliates using two distinct gene families.
• * To assess the utility of alpha-tubulin and phosphoglycerate kinase gene sequences for resolving ciliate evolutionary history.
• * To compare phylogenetic insights derived from different molecular markers.

Main Methods:

• * Comparative analysis of alpha-tubulin amino acid and nucleotide sequences from 20 ciliate species across seven classes.
• * Comparative analysis of phosphoglycerate kinase amino acid sequences from 7 ciliate species across three classes.
• * Phylogenetic tree construction and analysis.

Main Results:

• * Alpha-tubulin gene sequences did not provide informative resolution at the interclass level, yielding a bush-like tree with three main lineages (Hypotrichea, Oligohymenophorea, Litostomatea).
• * Phosphoglycerate kinase gene sequences showed a more promising branching pattern with three deeply separated branches, suggesting an early divergence of the Heterotrichea.
• * Congruence was observed between phylogenetic relationships inferred from both protein and rRNA sequence data at lower taxonomic and class levels.

Conclusions:

• * Phosphoglycerate kinase gene sequences appear more promising than alpha-tubulin for resolving interclass relationships within ciliates.
• * Phylogenetic analyses at lower taxonomic levels and class level are congruent across different molecular markers (protein and rRNA).
• * Further investigation using phosphoglycerate kinase is warranted for a more robust understanding of ciliate phylogeny.