Open Questions on the Origin of Eukaryotes

Area of Science:

• Cell Biology
• Evolutionary Biology
• Genomics

Background:

• The origin of eukaryotic cells (eukaryogenesis) remains a significant challenge in evolutionary biology.
• Endosymbiosis, particularly the acquisition of the mitochondrion from an alphaproteobacterial ancestor, is recognized as a critical event.
• The identity of the host cell in this endosymbiotic event is debated, with recent findings supporting archaeal origins.

Purpose of the Study:

• To review the current understanding of eukaryogenesis and the origin of the eukaryotic cell.
• To highlight the importance of archaeal lineages in understanding the host of the mitochondrial endosymbiont.
• To emphasize the need for integrated approaches combining phylogenomics and mechanistic studies of key eukaryotic innovations.

Main Methods:

• Phylogenomic analyses with expanded taxon sampling to identify prokaryotic relatives of eukaryotes.
• Investigation of plausible evolutionary mechanisms and selective pressures driving the emergence of eukaryotic features.
• Comparative analysis of the nucleus and bacterial-like eukaryotic membrane systems.

Main Results:

• The last eukaryotic common ancestor was likely a complex cell.
• Archaea-derived host models are increasingly supported by phylogenetic evidence.
• Understanding the evolution of the nucleus and membrane systems is crucial.

Conclusions:

• Resolving the origin of the eukaryotic cell requires robust phylogenomic data and mechanistic insights.
• Future research should focus on integrating phylogenetic discoveries with functional studies of early eukaryotic innovations.
• Archaea-derived hosts represent a promising avenue for understanding eukaryogenesis.