Award Date

5-1-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Life Sciences

First Committee Member

Allen Gibbs

Second Committee Member

Daniel Thompson

Third Committee Member

Mira Han

Fourth Committee Member

Don Price

Fifth Committee Member

Amei Amei

Number of Pages

134

Abstract

The Gibbs lab has maintained starvation-selected Drosophila melanogaster for >130 generations. These starvation-selected flies evolved an obese phenotype with a suite of physiological differences compared to control-fed flies. Previous studies have shown that long-term starvation-selected Drosophila contain more lipids, have lower metabolic rates and develop more slowly than controls. This dissertation encompasses 1) Examining the molecular mechanisms contributing to starvation resistance, 2) Functional validation of the candidate plin1 allele, and 3) Rapid physiological and genomic evolution in starvation-selected Drosophila.

Starvation-selected Drosophila survive starvation conditions much longer than control-fed flies. This study took a simple approach to identify possible differences in the nutrient-sensing pathways linked to candidate loci from Hardy et al. (2018). Specifically, I studied the key proteins in these pathways including: the lipoproteins PLIN1 and PLIN2, HSL, SIRT1 and dFOXO. My findings suggest differences in lipid storage during dietary restriction correlate with PLIN1 and HSL concentrations in the Drosophila fat body.

The plin1 locus was identified as a candidate for starvation resistance in previous studies (Hardy et al., 2018). Fed-control populations not exposed to starvation conditions had high frequencies for one of the two plin1 alleles (plin1FC), while starvation-selected populations evolved the alternate allele (plin1SS) to high frequencies. Functional assays from Chapter 2 document differences in PLIN1 concentrations in the starvation-selected flies compared to fed-control flies during starvation conditions. Brief characterization of the plin1SS allele identifies a 5’ UTR donor splice variant with possible impacts on the regulation of this locus. After generating homozygous lines for both alleles, I observed increased starvation survival time, mass and lipid content in homozygous plin1SS flies compared to plin1FC flies.

The candidate loci identified from previous studies provide important associations with the evolved phenotypes for starvation resistance, increased lipid content and decreased metabolism. However, it is difficult to directly link candidate loci with any of these phenotypes. This study used a novel time series E&R approach to directly associate the evolution of candidate loci with the evolution of starvation resistance, increased lipid content and decreased metabolism. I identify rapid physiological evolution for increased lipid content and starvation resistance in as early as one generation after selection. I observed that the underlying genomic evolution occurs via polygenic adaptation characterized by a core set of 169 candidate SNPs under constant selection.

Keywords

Drosophila melanogaster; Obese phenotype; Starvation resistance

Disciplines

Biology | Medical Physiology | Molecular Biology | Physiology

File Format

pdf

File Size

4.0 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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