By increasing genomic size, whole-genome duplication (WGD) is considered a major source of evolutionary innovation and speciation. We examined sequence evolution and expression divergence following WGD in a tetraploid African clawed frog (\textit{Silurana}). We hypothesized that the redundancy generated by WGD might allow for sex-specific and/or tissue-specific divergence, contributing to sexual dimorphism in this frog, and that such changes could be detected at both the expression and sequence levels. We investigated this hypothesis with a transcriptome-based approach, comparing both sexes across brain, heart and liver. We compared molecular evolution and expression divergence of duplicate gene homeologs to singleton genes and to an extant diploid relative, and identified genes with evidence for sex-biased expression. In doing so, we provide evidence for an allopolyploid mechanism of WGD and speciation in \textit{Silurana}. Additionally, we find that female-biased gene expression is more prevalent among duplicate genes than male-biased expression, particularly in brain where expression levels are highest. We similarly identified antagonistically sex-biased homeologs with indication of positive selection. Our results indicate that divergent evolution at both the sequence and expression levels following WGD favors the co-option of female-biased gene expression and may help resolve sexually antagonistic selection in this frog, thereby facilitating the evolution of sexual dimorphism. / Thesis / Master of Science (MSc) / Whole-genome duplication (WGD) is considered a major source of evolutionary innovation and a driver of speciation. By increasing genetic content and introducing redundancy, selective pressures are reduced and paralogous pairs diverge. We investigate how sex and tissue type contribute to duplicate gene divergence following WGD in a tetraploid African clawed frog. We find evidence for sex-dependent variation in sex-biased expression patterns of duplicate genes in brain, heart and liver, and evaluate how molecular evolution of duplicate genes accounts for expression divergence between sexes. This thesis provides a general framework for investigating sex-biased duplicate gene evolution in an amphibious tetrapod.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/18035 |
| Date | 11 1900 |
| Creators | Alcock, Brian |
| Contributors | Evans, Ben, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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