RESUMO
Wing pattern evolution in Heliconius butterflies provides some of the most striking examples of adaptation by natural selection. The genes controlling pattern variation are classic examples of Mendelian loci of large effect, where allelic variation causes large and discrete phenotypic changes and is responsible for both convergent and highly divergent wing pattern evolution across the genus. We characterize nucleotide variation, genotype-by-phenotype associations, linkage disequilibrium (LD), and candidate gene expression patterns across two unlinked genomic intervals that control yellow and red wing pattern variation among mimetic forms of Heliconius erato. Despite very strong natural selection on color pattern, we see neither a strong reduction in genetic diversity nor evidence for extended LD across either patterning interval. This observation highlights the extent that recombination can erase the signature of selection in natural populations and is consistent with the hypothesis that either the adaptive radiation or the alleles controlling it are quite old. However, across both patterning intervals we identified SNPs clustered in several coding regions that were strongly associated with color pattern phenotype. Interestingly, coding regions with associated SNPs were widely separated, suggesting that color pattern alleles may be composed of multiple functional sites, conforming to previous descriptions of these loci as "supergenes." Examination of gene expression levels of genes flanking these regions in both H. erato and its co-mimic, H. melpomene, implicate a gene with high sequence similarity to a kinesin as playing a key role in modulating pattern and provides convincing evidence for parallel changes in gene regulation across co-mimetic lineages. The complex genetic architecture at these color pattern loci stands in marked contrast to the single casual mutations often identified in genetic studies of adaptation, but may be more indicative of the type of genetic changes responsible for much of the adaptive variation found in natural populations.
Assuntos
Adaptação Fisiológica/genética , Borboletas/genética , Genética Populacional , Genoma/genética , Animais , Cromossomos Artificiais Bacterianos/genética , Regulação da Expressão Gênica , Loci Gênicos/genética , Variação Genética , Genótipo , Hibridização Genética , Desequilíbrio de Ligação/genética , Fases de Leitura Aberta/genética , Peru , Fenótipo , Mapeamento Físico do Cromossomo , Pigmentação/genética , Polimorfismo de Nucleotídeo Único/genética , Análise de Sequência de DNARESUMO
The neotropical butterflies Heliconius melpomene and H. erato are Müllerian mimics that display the same warningly colored wing patterns in local populations, yet pattern diversity between geographic regions. Linkage mapping has previously shown convergent red wing phenotypes in these species are controlled by loci on homologous chromosomes. Here, AFLP bulk segregant analysis using H. melpomene crosses identified genetic markers tightly linked to two red wing-patterning loci. These markers were used to screen a H. melpomene BAC library and a tile path was assembled spanning one locus completely and part of the second. Concurrently, a similar strategy was used to identify a BAC clone tightly linked to the locus controlling the mimetic red wing phenotypes in H. erato. A methionine rich storage protein (MRSP) gene was identified within this BAC clone, and comparative genetic mapping shows red wing color loci are in homologous regions of the genome of H. erato and H. melpomene. Subtle differences in these convergent phenotypes imply they evolved independently using somewhat different developmental routes, but are nonetheless regulated by the same switch locus. Genetic mapping of MRSP in a third related species, the "tiger" patterned H. numata, has no association with wing patterning and shows no evidence for genomic translocation of wing-patterning loci.
Assuntos
Adaptação Biológica/genética , Borboletas/fisiologia , Evolução Molecular , Genes de Insetos , Variação Genética , Asas de Animais/anatomia & histologia , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Biomimética , Padronização Corporal , Mapeamento Cromossômico , Cromossomos Artificiais Bacterianos , Cruzamentos Genéticos , Deriva Genética , Ligação Genética , Marcadores Genéticos , Fenótipo , Comportamento Predatório , Seleção Genética , Asas de Animais/fisiologiaRESUMO
ß-Hemolytic group C and group G streptococci (GCS-GGS; Streptococcus dysgalactiae subsp. equisimilis) emerged as human pathogens in the late 1970s. We report here the draft genome sequences of four genetically distinct human strains of GCS-GGS isolated between the 1960s and 1980s. Comparative analysis of these genomes may provide a deeper understanding of GCS-GGS genome and virulence evolution.