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The origin of the eukaryotic cell.
1Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge 02139, USA.
Speculations in Science and Technology
|January 1, 1984
Summary
The origin of eukaryotic cells may stem from an ancient RNA-based organism, not DNA-based ones. This RNA-first hypothesis explains key cellular structures and the prevalence of RNA viruses in eukaryotes.
Area of Science:
- Cell Biology
- Origin of Life Studies
- Evolutionary Biology
Background:
- The endosymbiotic hypothesis explains mitochondria and chloroplast origins.
- Mereschowsky (1905) suggested applying endosymbiosis to the nucleus.
- Eukaryotic cells exhibit unique RNA roles compared to prokaryotes.
Purpose of the Study:
- To propose an RNA-based origin for the host cell in eukaryotic evolution.
- To explain the presence of nucleus, mitochondria, and chloroplasts as endosymbionts.
- To investigate the role of RNA in early cellular structures and function.
Main Methods:
- Hypothetical modeling based on existing biological evidence.
- Comparative analysis of eukaryotic and prokaryotic cellular components.
- Review of endosymbiotic theory and RNA's role in cellular processes.
Main Results:
- An RNA-based host organism is a plausible precursor to eukaryotic cells.
- This hypothesis accounts for the nucleus, mitochondria, and chloroplasts as endosymbionts.
- Centrioles and basal bodies, lacking DNA, suggest an RNA-based origin for microtubule organizing centers (MTOCs).
Conclusions:
- The eukaryotic cell's origin likely involved an RNA-based organism engulfing DNA-based endosymbionts.
- This RNA-first model explains the abundance of RNA viruses and unique RNA functions in eukaryotes.
- Understanding this origin may clarify the evolutionary leap from prokaryotes to complex multicellular life.