Defense Date

7-5-2023

Graduation Date

Fall 12-15-2023

Availability

One-year Embargo

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

Committee Chair

Michael Jensen-Seaman

Committee Member

David Lampe

Committee Member

Wook Kim

Committee Member

Nathan Clark

Keywords

sexual selection, sperm competition, primates, TGM4, transglutaminase, sexual dimorphism

Abstract

Sexual selection is driven by the differential reproductive success of individuals, which is influenced by competition for mates and mate choice. In primates, this selective pressure has been attributed to the development of distinct anatomical, physiological, and behavioral characteristics. By employing comparative functional and genomic methodologies, this study aimed to assess the repercussions of primate sexual selection. To better understand the mechanisms driving sexually selected traits, an unbiased genome-wide analysis was used to associate rates of protein evolution with relative testes size and sexual size dimorphism. While previous research focused on the rapid evolution of male reproductive proteins in response to sexual selection, I detected strong conservation of testes-expressed proteins involved in male gamete generation and ciliary v form and function. Conversely, I found that the evolutionary rates of female reproductive proteins are accelerated in primates with large relative testes. I have also detected acceleration and conservation of proteins involved in the adaptive immune response, aligning with previous work suggesting an association between mating promiscuity and the evolution of pathogen defense genes. For functional analyses, I examined the prostate specific transglutaminase, TGM4, which is likely the driver of semen coagulation. The intensity of semen coagulation varies across primates, with some species forming a copulatory plug. Notably, TGM4 exhibits rapid evolution in chimpanzees, is nonfunctional in gorillas and gibbons, and is neutrally evolving or under relaxed constraint in humans. Using a mammalian expression system, recombinant human and chimpanzee TGM4 were expressed and tested in functional analyses. I found that chimpanzee TGM4 more readily crosslinks artificial substrates than human TGM4, which may be attributed to positive selection along the chimpanzee branch. Overall, the combination of genomic and functional analyses applied here demonstrate that sexual selection has impacted protein evolution leading to sequence variation and even functional differences between species.

Language

English

Included in

Evolution Commons

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