epistatic selection
Clark NL, Gasper J, Sekino M, Springer SA, Aquadro CF & Swanson WJ 2009 Coevolution of interacting fertilization proteins. PLoS Genet 5:e1000570.
- we studied female-male coevolution in the abalone by resequencing sperm lysin and its interacting egg coat protein, VERL, in populations of two species
- we found intergenic linkage disequilibrium between lysin and VERL, despite our demonstration that they are not physically linked
- we saw significant signs of association between lysin and VERL but not between non-interacting genes
- such tests between genes require measures to reduce intragenic linkage disequilibrium (LD) so that individual SNP comparisons will be more independent
- this is a significant challenge as intragenic LD can never be completely removed
- it can be reduced to low levels by using a tag SNP to represent each block of associated SNPs
- the proportion of significant comparisons between lysin and VERL remained high and statistically significant for all of these sets
- this observation supports an association between a sexually selected trait and preference for that trait
- the gene controlling preference (VERL) would select compatible alleles of the male trait (lysin)
- the observed association between lysin and VERL alleles formed prior to the latest selective sweep in lysin since it currently contains no amino acid polymorphisms
- according to this hypothesis we observed the residual LD between lysin SNPs that recombined onto the swept polymorphism
- indeed, the SNPs in LD with VERL are in the downstream portion of the lysin gene, away from the location of the putative selective sweep
- general studies of protein networks have revealed correlated rates of evolution for interacting proteins
- there is debate over how much of the correlation can be attributed to coevolution at the interaction interface or, instead, to shared selective pressures
- in the case of lysin and VERL, their divergence is driven predominantly at their sites of interaction
