Molecular evolution of a pervasive natural amino-acid substitution in Drosophila cryptochrome.
Genetic variations in circadian clock genes may serve as molecular adaptations, allowing populations to adapt to local environments. Here, we carried out a survey of genetic variation in Drosophila cryptochrome (cry), the fly's dedicated circadian photoreceptor. An initial screen of 10 European cry alleles revealed substantial variation, including seven non-synonymous changes. The SNP frequency spectra and the excessive linkage disequilibrium in this locus suggested that this variation is maintained by natural selection. We focused on a non-conservative SNP involving a leucine-histidine replacement (L232H) and found that this polymorphism is common, with both alleles at intermediate frequencies across 27 populations surveyed in Europe, irrespective of latitude. Remarkably, we were able to reproduce this natural observation in the laboratory using replicate population cages where the minor allele frequency was initially set to 10%. Within 20 generations, the two allelic variants converged to approximately equal frequencies. Further experiments using congenic strains, showed that this SNP has a phenotypic impact, with variants showing significantly different eclosion profiles. At the long term, these phase differences in eclosion may contribute to genetic differentiation among individuals, and shape the evolution of wild populations.
Department of Genetics, University of Leicester, Leicester, United Kingdom.
Mirko
M
Pegoraro
Department of Genetics, University of Leicester, Leicester, United Kingdom.
Shumaila
S
Noreen
Department of Molecular and Cellular Neurosciences, National Brain Research Centre, Manesar, Haryana, India.
Supriya
S
Bhutani
Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece.
Avgi
A
Tsolou
Department of Biochemistry, University of Leicester, Leicester, United Kingdom.
Ralf
R
Schmid
Department of Genetics, University of Leicester, Leicester, United Kingdom.
Charalambos P
CP
Kyriacou
Department of Genetics, University of Leicester, Leicester, United Kingdom.
Eran
E
Tauber
D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics*; D056931:Cryptochromes / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005060:Europe; D019143:Evolution, Molecular; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D006239:Haplotypes; D015810:Linkage Disequilibrium; D008297:Male; D008958:Models, Molecular; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D012641:Selection, Genetic
D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; C119828:cry protein, Drosophila