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Horizontal gene transfer among genomes: the complexity hypothesis
1Molecular Biology Institute and Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90095, USA.
Summary
Operational genes in prokaryotes transfer horizontally continuously, unlike informational genes. This continuous gene transfer, not early massive events, shapes prokaryotic evolution, driven by gene complexity, not evolutionary rates.
Area of Science:
- Genomics
- Evolutionary Biology
- Prokaryotic Genetics
Background:
- Horizontal gene transfer (HGT) is prevalent in prokaryotes.
- Operational genes (housekeeping) transfer more frequently than informational genes (transcription/translation).
Purpose of the Study:
- To test theories on the timing of HGT in prokaryotes.
- To investigate factors influencing differential HGT rates between gene types.
Main Methods:
- Phylogenetic analysis of six complete prokaryotic genomes.
- Identification of 312 sets of orthologous genes across these genomes.
Main Results:
- Operational genes show continuous HGT since prokaryotic divergence.
- No significant difference in evolutionary rates between operational and informational genes.
- Informational genes are often part of large, complex systems, hindering HGT.
Conclusions:
- HGT of operational genes is a continuous process, not limited to early evolutionary events.
- Gene complexity, rather than evolutionary rate, likely explains the differential HGT frequencies.
- The 'complexity hypothesis' proposes system integration as a barrier to informational gene HGT.