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Balancing selection at a frog antimicrobial peptide locus: fluctuating immune effector alleles?
Jacob A Tennessen1, Michael S Blouin
1Department of Zoology, Oregon State University, OR, USA. tennessj@science.oregonstate.edu
Molecular Biology and Evolution
|September 19, 2008
Summary
Antimicrobial peptides (AMPs) in leopard frogs show high genetic diversity due to fluctuating selection, not stable balancing selection. This diversity is crucial for host-pathogen coevolution and disease resistance.
Area of Science:
- Evolutionary biology
- Genetics
- Immunology
Background:
- Balancing selection is common in defense genes but rarely reported for immune effector proteins like antimicrobial peptides (AMPs).
- Understanding genetic diversity in AMPs is crucial for comprehending host-pathogen coevolution and disease resistance.
Purpose of the Study:
- To investigate the genetic diversity at a brevinin-1 AMP locus in three species of leopard frogs.
- To determine if balancing selection is responsible for the observed genetic diversity in AMPs.
Main Methods:
- Analysis of genetic diversity at the brevinin-1 AMP locus in Rana pipiens, Rana blairi, and Rana palustris.
- Application of population genetics tests including nonsynonymous/synonymous polymorphism ratio, ZnS test, and Tajima's D.
Main Results:
- Several highly divergent allelic lineages were found segregating at the brevinin-1 AMP locus.
- Evidence supports fluctuating selection, rather than stable balancing selection, as the driving force behind this diversity.
- Skewed allele frequencies, low synonymous variation, and divergent allele frequencies among populations indicate fluctuating selection.
Conclusions:
- AMP loci are significant reservoirs of adaptive genetic diversity.
- Fluctuating selection on AMPs has implications for host-pathogen coevolution.
- This genetic diversity enhances species' ability to resist disease epidemics.