Researchers in Japan have genetically transferred a unique courtship behavior from one fruit fly species to another. The achievement is the first example of behavior being transferred between species through single gene manipulation.
The project was a collaboration between Nagoya University and the National Institute of Information and Communications Technology (NICT).
In nature, male fruit flies generally court females by rapidly vibrating their wings thereby creating sounds – “courtship songs”. However, one species – Drosophila subobscura – has a different behavior: males regurgitate food and offer it as a gift to females during courtship. The team succeeded in transferring this behavior to another species, Drosophila melanogaster.
New connections in the brain
The two fruit fly species diverged about 30-35 million years ago. The researchers found the reason behind their different behavior during courtship. In gift-giving flies (D. subobscura), insulin-producing neurons are connected to the courtship control center in the brain, while in singing flies (D. melanogaster) these cells remain disconnected.
Further, the researchers focused on a specific gene, the fru gene, which is related to courtship behavior control in both species.
“When we activated the fru gene in insulin-producing neurons of singing flies to produce FruM proteins, the cells grew long neural projections and connected to the courtship center in the brain, creating new brain circuits that produce gift-giving behavior in D. melanogaster for the first time,” Dr. Tanaka Ryoya, co-lead author and lecturer at Nagoya University, explains.
Tracing genetic roots of behavior
The researchers further inserted DNA into D. subobscura embryos to create flies with heat-activated proteins in specific brain cells. They used heat to activate groups of these cells and compared the brains of flies that did and did not regurgitate food. They identified 16-18 insulin-producing neurons that make the male-specific protein FruM.
“Our findings indicate that the evolution of novel behaviors does not necessarily require the emergence of new neurons; instead, small-scale genetic rewiring in a few preexisting neurons can lead to behavioral diversification and, ultimately, contribute to species differentiation,” Dr. Hara Yusuke, co-lead author, NICT, notes.
“We have shown how we can trace complex behaviors like nuptial gift-giving back to their genetic roots to understand how evolution creates entirely new strategies that help species survive and reproduce,” senior author Dr. Yamamoto Daisuke, NICT, says.
Source: “First transfer of behavior between species through single gene manipulation,” press release, Nagoya University and NICT. The underlying study “Cross-species implementation of an innate courtship behavior by manipulation of the sex-determinant gene,” was published in the scientific journal Science.
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