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Protein-based phylogenies support a chimeric origin for the eukaryotic genome
1Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Molecular Biology and Evolution
|January 1, 1995
Summary
This study suggests eukaryotes originated from a mix of archaea and gram-negative bacteria, challenging traditional evolutionary trees. Protein sequence analysis reveals a chimeric origin for the eukaryotic cell nucleus.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genomics
Background:
- The evolutionary history and phylogenetic placement of Archaebacteria and Eukaryotes are subjects of ongoing scientific debate.
- Recent protein-sequence analyses have yielded unconventional phylogenies for these life forms, prompting further investigation.
Purpose of the Study:
- To investigate the phylogenetic relationships among major life forms using comprehensive protein-sequence data.
- To test the hypothesis of a chimeric origin for the eukaryotic cell nucleus.
Main Methods:
- Collected and analyzed available protein sequences from representatives of Gram-negative bacteria, Gram-positive bacteria, Archaebacteria, and Eukaryotes.
- Constructed monophyletic, unrooted phylogenies based on 24 distinct proteins.
- Evaluated statistical significance of observed phylogenetic clades.
Main Results:
- Phylogenetic analyses of seven out of 24 proteins revealed a significant Gram-positive-Archaebacteria / Gram-negative-Eukaryotic clade, contradicting the traditional three-way split.
- Nine proteins supported the conventional Gram-positive-Gram-negative / Archaebacteria-Eukaryotic clade.
- Eight proteins yielded statistically indistinguishable phylogenies.
Conclusions:
- The findings support a chimeric origin hypothesis for the eukaryotic cell nucleus.
- The eukaryotic nucleus may have formed through the fusion of an Archaebacterial and a Gram-negative bacterial ancestor.
- This challenges traditional models of early life evolution.