For the first time, scientists have induced asexual reproduction in an animal that usually reproduces sexually: the fruit fly Drosophila melanogaster. Once induced, the ability is passed on through the generations: the offspring can reproduce either sexually or asexually.
A paper describing the research appears in the journal Current Biology on July 28. The study's senior author is David Glover, research professor of biology and biological engineering. The research was carried out by Alexis Sperling, former postdoctoral fellow in Glover's laboratory at the University of Cambridge and a short-term visitor to Caltech, along with collaborators at the University of Tennessee.
For most animals, reproduction is sexual, involving a female's egg being fertilized by a male's sperm. Parthenogenesis, a type of asexual reproduction, is the process by which an egg develops into an embryo without fertilization by sperm-a male is not needed. While the offspring are not exact clones of their mother, they are genetically very similar and always female.
Certain species of fly, locusts, and chickens actually have the ability to switch between sexual reproduction and parthenogenesis. Switching to asexual reproduction can be a survival strategy to keep the species going if there are no males around.
Though the common laboratory fruit fly Drosophila melanogaster usually does not reproduce asexually, a distant species called Drosophila mercatorum that breeds on cacti does, in fact, have the ability to reproduce via parthenogenesis. Led by Cambridge postdoctoral scholar Alexis Sperling, the team studied D. mercatorum's genome and identified the genes underlying parthenogenesis. They then engineered the corresponding genes in D. melanogaster; the laboratory flies then gained the ability to reproduce asexually.
"It was truly stunning for us to find how tripping a small number of genetic switches would enable virgin Drosophila melanogaster fruit flies to generate viable and fertile offspring just like virgins of their distant Drosophila mercatorum cousins," says Glover. "It will be important to understand the generality of this ability, since many crop pests are able to reproduce in an asexual manner. Right now, we'd like to understand the molecular mechanisms underlying this cellular process in Drosophila melanogaster."
