Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Neuroscience

Supervisor

Moehring, Amanda J.

Abstract

Among sexually reproducing organisms, species are separated by their inability to reproduce with each other and form viable, fertile offspring. One type of reproductive barrier is behavioural, whereby mating is not initiated between two species. In the model organism Drosophila melanogaster, a gene called fruitless regulates heterospecific courtship and rejection behaviours, however, its neural mechanisms of action remain unknown in females. In this work, I identified which fruitless splice variants are expressed in adult males and females, and created the plasmid vectors necessary to implement a genetic system for the purposes of identifying, silencing, and hyperactivating neuronal subsets that express distinct splice-variants of fruitless. These plasmid vectors can be used in the future to induce expression of exogenous genes of interest for further experimentation in D. melanogaster.

Summary for Lay Audience

Speciation, the process by which populations diverge to form separate species, is initiated and reinforced by the emergence of barriers that inhibit reproductive success between populations that have sexual reproduction. These barriers are often physical abnormalities, such as genetic mutations that create offspring with defects that make them inviable or infertile. However, sometimes populations can also accumulate behavioural differences, and become separate species because they are no longer attracted to each other as viable mates.

The mechanisms behind behavioural barriers are less understood than their physical counterparts. However, in the model organism Drosophila melanogaster, a gene called fruitless (fru) influences behavioural isolation with its sister species. This gene is transcribed into many different mRNA products, with functions largely determined by the first and last sections of each transcript. In female D. melanogaster, the less-studied sex, expression patterns of each transcript were lesser known, and therefore transcripts that potentially affect female rejection behaviours could not be identified. I identified each fru transcript and profiled its expression in adult male and female D. melanogaster. I also identified the presence of a new non-sex-specific transcript that has not previously been described in the literature.

I then developed a series of DNA constructs that can be microinjected into Drosophila embryos for the integration of a Trojan-Gal4 system at specific locations in the fru gene. The Trojan-Gal4 system can be paired with other genetic tools to drive expression of desired genes in the same cells as the transcript of interest. The desired genes can be used to visualize, hyperactivate, and silence the neurons that express them, allowing for in-depth analysis of a transcript’s functions within the central nervous system, and on mating behaviours.

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