Virgin flies generate offspring in genetic experiment – 07/31/2023 – Science

Researchers from the United Kingdom and the United States have discovered the genetic recipe behind the ability to generate offspring without sex, the so-called parthenogenesis (something like “virgin birth” in Greek).

Armed with this data, they managed to make a species of fruit fly that normally only reproduces by crossing males and females generate viable offspring in this unusual way as well.

“We are the first to show that it is possible to induce virgin births in an animal. It was very exciting to see a virgin fly produce an embryo capable of developing to the adult stage and then repeating the process”, declared in an official statement the researcher Alexis Sperling, from University of Cambridge, who is the study’s first author. That is, the parthenogenetic capacity continued to exist in the following generations of that altered lineage.

Parthenogenesis can be found in several groups of invertebrates and also in reptiles, fish and other vertebrates. In general, the offspring generated by this method are genetically very similar to the mother, but not quite a clone of her. It is speculated that this possibility appears from time to time, over evolutionary time, in circumstances of scarce resources and/or partners.

To elucidate the genetic basis of parthenogenesis, Sperling and his colleagues took advantage of a “natural experiment”, the existence of a species of fruit fly (drosophila mercatorum) considered to be optional parthenogenetic. That is, there are groups of the species that reproduce normally by sex, while other lineages propagate through “virgin birth”.

A logical path, therefore, would be to investigate the differences between the two lineages. That’s what the British-American team did, analyzing DNA expression patterns – that is, which fly genes were “turned on” in different lineages. The list of differences between the two types of d. mercatorum it was huge, but it was possible to focus on a much smaller list of stretches of DNA that are linked to division processes and the integrity of cell structure and, as far as we know, could be important for parthenogenesis.

The next step was to manipulate versions of these genes in a distant relative of the fly that reproduces naturally by parthenogenesis. It’s about the Drosophila melanogastera species that has been used for about a century in genetic experiments of all kinds and, therefore, has biological characteristics very well known by scientists.

After testing a few different combinations of genes, the team realized that modifications to three of them were enough for a small percentage of the d. melanogaster become capable of parthenogenesis. “In the case of our genetically manipulated flies, the females waited around half of their lives – around 40 days – trying to find a male, but after that they gave up and ended up producing virgin offspring”, says the researcher from Cambridge.

The trio of genes includes Myc, which is important for the rapid cell multiplication typical of embryonic development. The other two genes, called polo and Desat2, are associated with more subtle aspects of the process, such as the structure of cells as they divide. In the process created in the laboratory, the unfertilized ovum of fruit flies can end up giving rise to offspring that are triploid —that is, they carry three copies of each set of DNA, and not two, as in the case of humans and the vast majority of animals.

Studying how the process works, in addition to unraveling a biology enigma, can also have positive impacts on the control of agricultural pests, since many of these insects can end up developing parthenogenesis.