Scientists discover virgin birth secret — alters an animal to have it too

Genetically engineered female flies, tired of waiting for a male, give up and opt for virgin birth.
Sade Agard
Researchers have identified the genes that are switched on, or switched off, when these flies reproduce without fathers.
Researchers have identified the genes that are switched on, or switched off, when these flies reproduce without fathers.

Jose Casal and Peter Lawrence 

Scientists have achieved a significant milestone by identifying a genetic trigger for virgin birth in an animal species that typically reproduce sexually, according to a study published in Current Biology on July 25. 

The fruit fly Drosophila melanogaster has become the first animal in which researchers successfully induced virgin birth, which now can pass this down to future female generations.

Whatsmore, the offspring display remarkable reproductive flexibility, capable of engaging in sexual reproduction in the presence of males or resorting to virgin birth when males are absent.

What happens in Virgin Birth?

In most animals, reproduction involves fertilizing a female's egg with a male's sperm. However, virgin birth, scientifically known as parthenogenesis, is a unique process where an egg develops into an embryo without being fertilized by sperm, rendering the presence of a male unnecessary. 

Notably, offspring resulting from virgin birth are not exact clones of their mother but share close genetic similarities and are consistently female.

“We’re the first to show that you can engineer virgin births to happen in an animal – it was very exciting to see a virgin fly produce an embryo able to develop to adulthood, and then repeat the process,” said first author Dr Alexis Sperling, a researcher at the University of Cambridge in a press release.

“In our genetically manipulated flies, the females waited to find a male for half their lives - about 40 days - but then gave up and proceeded to have a virgin birth," she added. 

This ability for virgin birth can be a survival strategy for species. In specific circumstances, a generation of virgin births can ensure the continuation of a species when sexual reproduction is not immediately feasible.

The breakthrough involved sequencing the genomes of two strains of another fruit fly species, Drosophila mercatorum. One strain relied on males for reproduction, while the other was exclusively capable of virgin birth. 

By identifying the genes responsible for the virgin birth ability in Drosophila mercatorum, the researchers successfully altered the corresponding genes in the model fruit fly, Drosophila melanogaster, thereby inducing virgin birth in the latter species.

Importantly, Drosophila melanogaster was key to this discovery. It has been a widely used "model organism" in genetics research for over a century, with its genes extensively understood. 

220,000 virgin fruit flies

The research, involving over 220,000 virgin fruit flies, spanned six years and required immense dedication.

While virgin birth is observed naturally in some egg-laying animals like birds, lizards, and snakes, it is rare in species that predominantly reproduce sexually. 

Instances of virgin birth in sexually reproducing animals are often only seen in isolated zoo animals with limited opportunities to find mates.

The implications of this research extend beyond the realm of fruit flies. The ability to understand and induce virgin birth could provide crucial insights into pest control strategies in agriculture. 

For instance, “If there’s continued selection pressure for virgin births in insect pests, which there seems to be, it will eventually lead to them reproducing only in this way," explained Dr. Sperling, who spearheaded this work in the Department of Genetics.

"It could become a real problem for agriculture because females produce only females, so their ability to spread doubles," she concluded.

The complete study was published in Current Biology on July 25 and can be found here.

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