Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Date of Graduation
5-9-2024
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Biology
Second Advisor
Jaíra Ferreira de Vasconcellos
Third Advisor
Marquis Walker
Abstract
The skin is the key organ regulating the animal-environment interface and is particularly sensitive to the abiotic factors of temperate environments, such as extreme cold and aridity during winter. Previous research found that, in the skin, temperate birds and reptiles upregulate expression of lipid synthesis genes to prevent tissue freezing and evaporative water loss in winter. My study species, the red-sided garter snake (Thamnophis sirtalis parietalis), has seasonally variable skin lipid composition, and females produce a modified set of these lipids that function as a sex pheromone. The pheromone is maximally produced in the spring breeding season following prolonged, low-temperature dormancy (~8 months at 2-4°C). The snakes experience dramatic physiological changes in gene expression in many tissues after approximately 12 weeks spent in hibernation. Also, at least one tissue in this species has temperature-sensitive gene expression (sex regions of the brain), which implies similar sensitivities in gene expression exist in other tissues associated with reproduction, such as skin. Production and modification of skin lipids in vertebrates is achieved by a series of enzymes, yet much remains elusive regarding seasonal and sexual variation in said gene expression. I investigated the influence of sex and season on expression of lipid synthases (ACAC, FASN, ELOVL1) and desaturases (FADS1, SCD) in the skin of male and female red- sided garter snakes across their active period (spring, summer, fall) and in males through dormancy using quantitative PCR. Overall expression in both sexes was high in spring and suppressed in summer. Upregulation occurred in males in fall, seemingly responding to cooling, whereas females did not. Additionally, most genes demonstrated strong co- expression, which may suggest sex-specific pathway dynamics in the skin. Through dormancy, gene expression remained unchanged in males, yet dynamic shifts in gene correlations were observed over time, becoming maximal by week 12. My findings are the first to reveal how skin lipid metabolism operates at the molecular level in reptiles, and how it may influence sex-specific reproductive strategies and enable animals to cope with conditions associated with extreme environments.
