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Gene order constrains adaptation in bacteriophage T7
R Springman1, M R Badgett, I J Molineux
1Section of Integrative Biology, University of Texas, Austin, TX 78712, USA.
Virology
|August 6, 2005
Summary
Gene order impacts bacteriophage fitness. Experiments show that even with mutations, reorganized genomes struggle to regain wild-type fitness, highlighting the functional significance of gene arrangement.
Area of Science:
- Genomics
- Molecular Biology
- Evolutionary Biology
Background:
- The functional significance of gene order in genomes is widely hypothesized but experimentally underexplored.
- Gene arrangement is believed to influence gene regulation and organismal fitness.
Purpose of the Study:
- To experimentally test the importance of gene order for bacteriophage fitness.
- To investigate the ability of a bacteriophage T7 variant with an ectopically positioned RNA polymerase gene to regain wild-type fitness.
Main Methods:
- Adaptation of a bacteriophage T7 variant with a repositioned RNA polymerase gene.
- Maintenance of two replicate lines with the original gene order and observation of mutations.
- Analysis of a third replicate line that evolved a new gene order through recombination.
Main Results:
- Lines maintaining the original gene order showed modest fitness recovery despite numerous mutations.
- A mutation in the early terminator signal accounted for most fitness recovery in these lines.
- A third line evolved a new gene order, achieving higher fitness but still below wild-type levels.
Conclusions:
- Gene order is crucial for bacteriophage fitness.
- Reorganized genomes do not rapidly re-evolve wild-type fitness.
- Specific mutations, like those in terminator signals, and recombination significantly impact fitness recovery.