Male pheromones induce early removal of mating plug and promote re-mating in Drosophila females

Core Concepts

Male pheromones 2-methyltetracosane and 7-Tricosene shorten the ejaculate holding period in mated Drosophila females, enabling them to remove the mating plug earlier and engage in re-mating more readily.

Abstract

The study investigates how changes in the social sexual context influence the ejaculate holding period (EHP) in Drosophila females. It was found that the presence of courting males after mating significantly shortens the EHP, a phenomenon termed "male-induced EHP shortening (MIES)". MIES is mediated by the detection of two male pheromones - 2-methyltetracosane (2MC) and 7-Tricosene (7-T) - through the olfactory receptor Or47b and the gustatory receptor ppk23, respectively. These pheromones converge on a subset of pC1 neurons in the female brain, increasing their cAMP levels. The elevated cAMP transiently enhances the excitability of pC1 neurons, enabling mated females to promptly remove the mating plug and engage in re-mating more readily. The study establishes MIES as a genetically tractable model for understanding the neural mechanisms underlying sexual plasticity in response to changes in the social sexual context.

Stats

The presence of courting males after mating shortens the ejaculate holding period (EHP) in females by approximately 30 minutes. Silencing Or47b-expressing olfactory receptor neurons or Or47b receptor gene abolishes the male-induced EHP shortening. Incubation with 750 ng of the male pheromone 2-methyltetracosane (2MC) shortens the EHP in wild-type females, but not in Orco or Or47b mutant females. Silencing ppk23-expressing gustatory neurons also abolishes the male-induced EHP shortening. Optogenetic activation of the pC1b and pC1c neuron subset increases cAMP levels and shortens the EHP, while activation of pC1a or pC1d/e does not.

Quotes

"Notably, the EHP of females incubated with naive males was approximately 30 minutes shorter than that of females left in isolation after mating." "Our findings revealed that silencing ORNs expressing Or13a, Or19a, Or23a, Or47b, Or65c, Or67d or Or88a significantly impacted MIES." "Activation of these neurons with the thermogenetic activator dTRPA1 resulted in a significant EHP shortening, even in the absence of male exposure."

Key Insights Distilled From

Male cuticular pheromones stimulate removal of the mating plug and promote re-mating through pC1 neurons in Drosophila females

by Yun,M., Kim,... at www.biorxiv.org 11-28-2023

https://www.biorxiv.org/content/10.1101/2023.11.28.568981v2

Deeper Inquiries

How do the levels of 2MC and 7-T in males vary under different environmental and physiological conditions, and how might this impact their ability to induce MIES in females?

The levels of 2MC and 7-T in males can vary under different environmental and physiological conditions. For example, exposure to low temperatures during development has been linked to increased production of both 2MC and 7-T. Similarly, the mutation of certain genes, such as the desiccation stress gene CG9186, can impact the levels of 2MC. Additionally, 2MC levels have been found to increase with the aging of males. These variations in 2MC and 7-T levels can impact their ability to induce Male-Induced EHP Shortening (MIES) in females. The levels of 2MC and 7-T serve as indicators of male age and resilience against environmental stresses. Higher levels of these pheromones may signal qualities that make males more attractive to females. Therefore, under conditions where males have higher levels of 2MC and 7-T, they may be more successful in inducing MIES in females, leading to a shorter ejaculate holding period and increased receptivity to further mating.

What other neural pathways, beyond the pC1 neurons, might be involved in regulating the ejaculate holding period and female sexual plasticity in response to social cues?

In addition to pC1 neurons, other neural pathways may be involved in regulating the ejaculate holding period and female sexual plasticity in response to social cues. One potential pathway could involve the neuropeptide Dh44 and its receptor neurons in the brain pars intercerebralis (PI). Dh44 has been shown to regulate the timing of sperm ejection or ejaculate holding period. Another pathway could involve sensory neurons that detect additional pheromones or environmental cues, influencing female receptivity and mating behavior. Additionally, circuits involved in processing auditory and visual cues related to courtship and social interactions may play a role in modulating female sexual behavior in response to changing social contexts.

Could the insights from this study on the neural mechanisms of sexual plasticity in Drosophila be applied to understand similar phenomena in other animal species, including vertebrates?

The insights gained from studying the neural mechanisms of sexual plasticity in Drosophila can be applied to understand similar phenomena in other animal species, including vertebrates. Many aspects of social and sexual behaviors are conserved across different species, making Drosophila an informative model for studying these behaviors. The neural circuits and molecular pathways identified in Drosophila, such as the involvement of specific neurons like pC1 in regulating female mating receptivity, may have homologous counterparts in vertebrates. By studying the genetic and neural basis of sexual plasticity in Drosophila, researchers can gain a deeper understanding of how social cues and environmental factors influence reproductive behaviors. This knowledge can then be extrapolated to vertebrate species to explore the evolutionary and functional aspects of sexual plasticity across different taxa. Ultimately, the findings from Drosophila studies can provide valuable insights into the neural mechanisms underlying sexual behaviors in a wide range of animal species.