Study on Hormone-Neuropeptide Pathway Inhibiting Sexual Receptivity in Immature Drosophila Females

Academic Background

Sexual maturation is a critical developmental event in the transition from juvenile to adult, accompanied by multiple physiological and behavioral changes. In Drosophila, the process of transition from an asexual state to sexual maturity in females has not been fully elucidated, especially the role of hormones and neuromodulators in this process. Although it is known that hormones such as ecdysone and juvenile hormone (JH) play important roles in insect development, how they regulate sexual behavior during sexual maturation remains unclear. Additionally, neuropeptides have also garnered significant attention for their role in regulating sexual behavior. This study aims to reveal how hormones and neuropeptides coordinate sexual receptivity during the sexual maturation of female Drosophila, particularly the role of the ecdysone-neuropeptide leucokinin (LK)-leucokinin receptor (LKR) pathway.

Source of the Paper

This paper was co-authored by Jie Chen, Peiwen Zhu, Sihui Jin, Zhaokun Zhang, Simei Jiang, Sheng Li, Suning Liu, Qionglin Peng, and Yufeng Pan, from institutions including the School of Life Science and Technology at Southeast University and the Institute of Insect Science and Technology at South China Normal University. The paper was published in PNAS (Proceedings of the National Academy of Sciences) on February 21, 2025, titled “A hormone-to-neuropeptide pathway inhibits sexual receptivity in immature Drosophila females.”

Research Process and Results

1. Research Process

1.1 Determination of the Time Points of Sexual Transition in Female Drosophila

The study first observed the sexual receptivity behavior of wild-type female Drosophila (Canton-S and w1118 strains) from 6 hours to 7 days post-eclosion to determine the time points of the transition from an asexual state to sexual maturity. The results showed that females were almost non-receptive to male courtship within the first 18 hours post-eclosion, but the receptivity rate gradually increased after 18 hours and peaked at 3 days.

1.2 Role of LK Neuropeptide During Sexual Transition

By screening mutants of 16 neurotransmission-related genes, the study found that females with leucokinin (LK) mutations exhibited significantly higher receptivity rates at 36 hours compared to wild types. Further generation of LK gene deletion mutants (δlk1 and δlk2) using CRISPR/Cas9 technology confirmed the specific role of LK in inhibiting sexual receptivity in immature females.

1.3 Functional Study of LK Neurons

Using LK-Gal4 to drive labeling of LK neurons and activating LK neurons via temperature-sensitive ion channel dTRPA1, the study found that activation of LK neurons significantly inhibited sexual receptivity in females at 36 hours and 7 days. Further restriction of LK-Gal4 expression using brain-specific Flippase recombinase (otd-flp) revealed that LK neurons in the subesophageal zone (SEZ) and abdominal (ABLK) regions play a key role in suppressing sexual receptivity.

1.4 Regulation of LK Neurons by Ecdysone

The study knocked down the ecdysone receptor (EcR) gene in LK neurons through RNA interference (RNAi), finding that knockdown of EcR-A and EcR-B1 significantly increased receptivity in 36-hour females. Additionally, exogenous 20-hydroxyecdysone (20E) significantly increased calcium signals in LK neurons, indicating that ecdysone suppresses sexual receptivity by enhancing LK neuron activity.

1.5 LK Functions Through Its Receptor LKR in PC1 Neurons

The study labeled LKR-expressing neurons via LKR-Gal4 and knocked down LKR expression, finding that LKR knockdown significantly increased receptivity in 36-hour females. Further knockdown of LKR expression driven by PC1-SS1 confirmed that LK suppresses sexual receptivity through LKR in PC1 neurons.

2. Main Results

• Time Points of Sexual Transition: Females are almost non-receptive to male courtship within the first 18 hours post-eclosion; receptivity gradually increases after 18 hours and peaks at 3 days.
• Role of LK: LK mutant females exhibit significantly higher receptivity rates at 36 hours compared to wild types, indicating that LK specifically inhibits sexual receptivity during sexual transition.
• Function of LK Neurons: Activation of LK neurons significantly inhibits sexual receptivity in females at 36 hours and 7 days, and this inhibition depends on the release of LK peptides.
• Regulation by Ecdysone: Ecdysone enhances LK neuron activity through the EcR receptor, thereby suppressing sexual receptivity.
• LK-LKR-PC1 Pathway: LK functions through its receptor LKR in PC1 neurons to inhibit sexual receptivity.

3. Conclusion

This study reveals a hormone-neuropeptide pathway (ecdysone-LK-LKR) that specifically inhibits sexual receptivity during the sexual maturation of female Drosophila. This discovery not only elucidates the synergistic role of hormones and neuropeptides in regulating sexual behavior but also provides new insights into the neural mechanisms of sexual maturation.

4. Highlights of the Study

• Key Findings: First revelation of the inhibitory role of the ecdysone-LK-LKR pathway during the sexual maturation of female Drosophila.
• Methodological Innovation: Use of CRISPR/Cas9 technology to generate LK and LKR gene deletion mutants, combined with optogenetics and calcium imaging techniques to study neuronal activity regulation.
• Scientific Value: Provides a new theoretical framework for studying the neural mechanisms of sexual maturation and potential applications in regulating insect sexual behavior.

5. Other Valuable Information

This study also found that LK neurons are not only involved in regulating sexual receptivity but may also play multiple roles in other behaviors (such as feeding and sleep). This finding provides directions for further research into the multifunctionality of LK.

Summary

Through systematic experimental design and advanced technical methods, this study reveals the inhibitory role of the ecdysone-LK-LKR pathway during the sexual maturation of female Drosophila. This discovery not only deepens our understanding of the neural mechanisms of sexual maturation but also provides new research ideas for regulating insect sexual behavior.