Why Study Fly Sex?

If you talk about "fly sex" at a party, you're likely to attract some quizzical glances. But aside from its entertainment value, you might wonder why a lab would choose to study reproduction in an insect like Drosophila. Happily, there are many reasons why studying a fundamental biological process (like reproduction) in a model organism (like Drosophila) is both important and interesting!

1. Research about Drosophila reproduction is highly relevant to the control of insect disease vectors and agricultural pests.

The species we study, Drosophila melanogaster, is closely related to other insects that are of extreme importance for human health and agriculture. Mosquito species that cause malaria, dengue fever or Zika virus have similar suites of reproductive proteins and post-mating behaviors to those observed in D. melanogaster, and methods we have developed in fruit flies have been transferable to these systems. An even closer relative, Drosophila suzukii, is an agricultural pest that is currently spreading across American orchards. Insights we gain from studying the safe and accessible D. melanogaster system may help researchers of these pests develop methods to combat their spread.

2. The types of proteins involved in Drosophila reproduction are similar to those involved in mammalian reproduction.

Comparative genomics has revealed that there are only so many ways to concoct animal seminal fluid. While the exact "ingredients" (proteins) in Drosophila seminal fluid are different from those of rodents and humans, the types of proteins (e.g., proteolysis regulators, immune modulators, peptide hormones, carbohydrate-binding proteins) are conserved. Thus, if we understand how different types of proteins interact in fly seminal fluid, it may help generate hypotheses about how these proteins interact in mammals. This question is important because, just like in flies, mammalian seminal fluid proteins are essential for fertility.

3. The tools we use to study Drosophila reproduction are directly applicable to many other biological processes and organisms.

Our research uses numerous tools that are broadly applicable. For example, one evolutionary method that we use to predict reproductive protein interactions was originally designed for yeast and is now being applied to predict genes that cause human disease. A proteomic method that we developed to identify reproductive proteins in flies has been successfully applied to mice. We also use RNA interference (RNAi) and CRISPR/Cas9 genome editing, modern technologies for genetic manipulation in many animal systems (including human cell culture). For a good example of how Drosophila RNAi screens can lead to insights about human disease, check out this article that used an RNAi screen in flies to find a new gene important for cardiac function in humans. By using these broadly applicable methods in a fast-growing, easily manipulated model system, we can refine and improve the methods to the benefit of the greater scientific community.

4. Drosophila is a highly tractable experimental system in which to ask fundamental questions about evolutionary biology.

Reproduction is an essential topic in evolutionary biology because it is central to an organism's fitness -- in fact, Charles Darwin wrote much of a book on the subject. Modern day evolutionary biologists study reproduction and sexual selection in a menagerie of organisms, but few of these organisms rival Drosophila melanogaster for the ease of experimental manipulation. Using Drosophila, we can directly mutate the genes that have been subject to recent selection. By doing so, we can determine these genes' functions and thus understand why selection has targeted these particular genes.

5. Through researching flies, students can gain essential, transferable skills in genetics and the general scientific method.

Drosophila also has great value as a pedagogical tool for students who are learning biology. Because flies are easy to work with and have a fast generation time, students rapidly come to appreciate the power of genetic analysis, which is used in labs in all areas of biology. Our behavioral experiments rely heavily on fundamental principles of experimental design, such as randomization, reproducibility, the use of proper controls, blinding, and the choice of appropriate statistical analyses. Drosophila melanogaster also has an exceptionally well-curated genome, allowing students to gain familiarity with genomic concepts that are becoming ever more applicable across biology.

6. Many discoveries from basic science research are later found to be highly applicable to biomedical problems.

Basic science research is important in its own right because it helps us better understand the natural world that surrounds us. But history also shows that many discoveries that had no immediate "medical relevance" have become invaluable for their contributions to biomedical knowledge. In the field of reproduction, the characterization of a protein required for sea urchin sperm to recognize an egg led to insights about the function of a protein implicated in human polycystic kidney disease. Similarly, it was only recently discovered that proteins mediating the fusion of two yeast cells, the meeting of gametes in a marine mollusk, and the interactions of human sperm and eggs all share a common evolutionary origin. More broadly, Nobel Prizes have been awarded for studies of glowing green jelly fish, chromosome maintenance in pond-dwelling protists, and muscle protein function in roundworms. The researchers studying these processes were doing so not to cure cancer or heart disease, but because they were interested in how life works. As they and others would soon find, though, the processes they discovered and the methods they used turned out to have profound implications for health and biomedical research. These examples are not meant to suggest that studies of fly sex are going to win a Nobel Prize. But, they do suggest that cultivating a broad and deep pool of basic scientific knowledge is important, because it's impossible to tell when this knowledge will become important for health or society!