Abstract
In birds and insects, the female uptakes sperm for a specific duration post-copulation known as the ejaculate holding period (EHP) before expelling unused sperm and the mating plug through sperm ejection. In this study, we found that Drosophila melanogaster females shortens the EHP when incubated with males or mated females shortly after the first mating. This phenomenon, which we termed male-induced EHP shortening (MIES), requires Or47b+ olfactory and ppk23+ gustatory neurons, activated by 2-methyltetracosane and 7-tricosene, respectively. These odorants raise cAMP levels in pC1 neurons, responsible for processing male courtship cues and regulating female mating receptivity. Elevated cAMP levels in pC1 neurons reduce EHP and reinstate their responsiveness to male courtship cues, promoting re-mating with faster sperm ejection. This study established MIES as a genetically tractable model of sexual plasticity with a conserved neural mechanism.
Significance Statement Sexual plasticity, the adaptation of reproductive behavior to social changes, was explored in the fruit fly, a genetically tractable model insect. Our findings revealed that inseminated females, encountering another courting male post-mating, shorten the ejaculate holding period (EHP). Specific olfactory and gustatory pathways regulating this phenomenon were identified, converging on the pC1 neurons in the brain-a conserved neural circuit that regulates female mating activity. Odors associated with EHP shortening increased the second messenger cAMP. The transient elevation of cAMP heightened the excitability of pC1 neurons, facilitating the prompt removal of the male ejaculate and subsequent re-mating . This study established a behavioral model of sexual plasticity and provided a framework for understanding the neural circuit processes involved.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
In the revised manuscript, we made the following changes. 1.We provided new evidence that Or47b is required for 2MC-induced cAMP increase in pC1 neurons, but not for 7T-induced increase. This observation supports that Or47b functions as a receptor for 2MC. 2.We showed the expression of the pC1a-split-Gal4 transgene in the brain and VNC. 3.We prepared a new figure summarizing the results and explaining the current working model.4.We clarified the comparisons made in the multiple comparison analysis and specified the tests used in several figures.5.We corrected typographical errors and made some changes to improve readability.