When male and female fruit flies age, their brains become desexualized. Age-related changes occur in both sexes, but the male brain is feminized to a greater extent than the female brain. This is the conclusion of a study by a research group at Linköping University. The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.
It is a well-known fact that weaker individuals cannot afford to ‘invest’ in sexual behavior to the same extent as their healthier counterparts. However, it is not clear whether aging, which weakens individuals, also leads to a decreased investment in sexual activity. You might think that for individuals approaching the end of their lives, it would be best to go ‘all in’ on reproduction, to pass on their genes before it’s too late. Sexual behavior is controlled from the brain, and to find out what happens to sex differences in this tissue as fruit flies age, the researchers examined how genes expressed to different degrees in young men and women change over time. change.
“Our results show that gene expression in male and female brains become more similar with age, and that both sexes contribute to this pattern,” said Dr. Antonino Malacrinò, one of the lead authors of the study who now works at the University of Reggio Calabria in Italy.
What the study shows is that if the expression of a particular gene is higher in the brains of young women than in young men, the expression of the gene is reduced in older women and increased in old men — and vice versa for genes with a higher expression in young men.
“The results also show that the changes are greater in men than in women,” says Antonino Malacrinò.
The fact that women change less with age than men is probably due to the fact that the association between investing in sexual characteristics and reproductive success is not as strong in women as in men. While in order to reproduce, a male fruit fly must outperform other males by quickly finding females and encouraging them to mate through an intricate and taxing dance performance, a female needs only to decide how much energy she has available for reproduction. . Aging means fewer resources are available to invest in reproduction and other activities for both sexes, but fierce competition between men means that the cost of higher investment is higher for them than for women.
“If you keep investing in reproduction as much as you did before, you’ll run out of energy to survive,” said Urban Friberg, who led the research and is a senior associate professor in the Department of Physics, Chemistry and Biology. (IFM) at Linköping University.
Studies in other animals, including humans, that have mainly focused on age-related changes in gene expression in one sex have produced results pointing in the same direction. This indicates that the results shown in fruit flies may also apply to many other animals.
“We get the same general results in both populations of fruit flies that we studied, even though they differ quite a bit in which genes are involved,” says Urban Friberg.
The results of the study are reminiscent of those of the group in a previous study. In that study, sex differences in gene expression were compared between male and female flies of high and low genetic quality. Similar to how aging reduces sex differences, the earlier study showed that reduced genetic quality makes gene expression more similar in male and female flies, and again it was males who altered their gene expression more than females.
The study does not answer which molecular signal associated with aging lies behind the reduced sex differences in the brain. Further research on this topic could be rewarding, especially if the signaling molecule were found to be shared with other species.
Picky female fruit flies reproduce anyway
Aging desexualizes the Drosophila brain transcriptome, Proceedings of the Royal Society B: Biological Sciences (2022). DOI: 10.1098/rspb.2022.1115. rspb.royalsocietypublishing.or … .1098/rspb.2022.1115
Provided by the University of Linköping
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