The modulatory effects of biogenic amines on male mating performance in Bactrocera dorsalis

Molecular and pharmacological characterization of the dopamine receptors in the oriental fruit fly, Bactrocera dorsalis

Dopamine (DA) is a critical molecule within the insect nervous system, known to regulate a myriad of physiological functions and instigate behavioral shifts in insects. It exerts its effects by interacting with specific dopamine receptors (DARs). In this study, three DARs cDNAs from Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) (BdDOP1, BdDOP2 and BdDOP3) were cloned using molecular biology techniques. These receptors exhibited high sequence identity with their orthologous DARs, and phylogenetic analyses also clustered these receptors within their respective receptor subtype. Additionally, the high expression levels of these DARs in the head suggest their prominent role in the central nervous system of B. dorsalis. To investigate the pharmacological properties of these receptors, expression vectors for BdDOP1, BdDOP2 and BdDOP3 were constructed and expressed in HEK-293T cells. Our results demonstrated that DA and synthetic agonists activated these receptors in a dose-dependent manner, and DA activation can be competitively inhibited by various antagonists, exhibiting distinct potencies for each dopamine receptor type. Among the tested antagonists, SCH-23390, methiothepin, and metoclopramide were identified as the most potent inhibitors of BdDOP1, BdDOP2 and BdDOP3, respectively. This study provides valuable insights into the molecular and pharmacological characteristics of DARs in B. dorsalis, offering a theoretical foundation for the development of novel behavioral modulators targeting these receptors. The findings also serve as a reference for the functional analyses of DARs in other insect species.

Activation of mating-related behavior by serotonin in males of the Japanese yellow hornet Vespa simillima

The behavioral physiology of males in social wasps has received little attention, despite the importance of male behavior adapted to complex social environments. To explore the roles of brain biogenic amines in mating-related behavior in male Japanese yellow hornets (Vespa simillima), we first determined the development of mating-related behavior and age-related changes to biogenic amines in the brain. The activities of locomotion, flight, and mating in the males increased with day-age by 1 week after emergence. Testes size decreased within 1 week after adult emergence, suggesting that male sexual maturation may be complete with the development of mating-related behavior. Serotonin levels in the brain increased with age in parallel to the behavioral activities. Dopamine levels in the brain peaked at 2 days of age and then decreased with age, whereas octopamine levels in the brain decreased with age. Thus, serotonin was a candidate compound activating mating-related behavior in males. We then examined the effects of serotonin on the mating-related behavior of males using serotonin injections. Injections of serotonin significantly enhanced activities of locomotion, flight, and mating, depending on serotonin concentration. Those results suggested that serotonin activates mating-related behavior in male hornets.

OBP83b and OBP49a Involved in the Perception of Female-Derived Pheromones in Bactrocera dorsalis (Hendel)

In Bactrocera dorsalis, both males and females release chemical signals to attract mates. In our previous study, we identified ethyl laurate, ethyl myristate, and ethyl palmitate as potent female-derived pheromones that contribute to mate attraction. However, the mechanisms underlying the olfactory recognition remain unclear. In this study, we observed strong antennal and behavioral responses in male B. dorsalis to these female-derived pheromones, and further investigation revealed significant upregulation of OBP49a and OBP83b following exposure to these compounds. Through fluorescence competitive binding assays and RNA interference techniques, we demonstrated the crucial roles of OBP49a and OBP83b in detecting female-derived pheromones. Finally, molecular docking analysis identified key residues, including His134 in OBP83b and a lysine residue in OBP49a, which formed hydrogen bonds with female-derived pheromones, facilitating their binding. These findings not only advance our understanding of olfactory recognition of pheromones in B. dorsalis but also offer potential targets for developing olfaction-interfering techniques for pest control.

Serotonergic amplification of odor-evoked neural responses maps onto flexible behavioral outcomes

Behavioral responses to many odorants are not fixed but are flexible, varying based on organismal needs. How such variations arise and the role of various neuromodulators in achieving flexible neural-to-behavioral mapping is not fully understood. In this study, we examined how serotonin modulates the neural and behavioral responses to odorants in locusts (Schistocerca americana). Our results indicated that serotonin can increase or decrease appetitive behavior in an odor-specific manner. On the other hand, in the antennal lobe, serotonergic modulation enhanced odor-evoked response strength but left the temporal features or the combinatorial response profiles unperturbed. This result suggests that serotonin allows for sensitive and robust recognition of odorants. Nevertheless, the uniform neural response amplification appeared to be at odds with the observed stimulus-specific behavioral modulation. We show that a simple linear model with neural ensembles segregated based on behavioral relevance is sufficient to explain the serotonin-mediated flexible mapping between neural and behavioral responses.

Plasticity of the olfactory behaviors in Bactrocera dorsalis under various physiological states and environmental conditions

Insects rely heavily on their olfactory system for various behaviors, including foraging, mating, and oviposition. Numerous studies have demonstrated that insects can adjust their olfactory behaviors in response to different physiological states and environmental conditions. This flexibility allows them to perceive and process odorants according to different conditions. The Oriental fruit fly, Bactrocera dorsalis, is a highly destructive and invasive pest causing significant economic losses to fruit and vegetable crops worldwide. The olfactory behavior of B. dorsalis exhibits strong plasticity, resulting in its successful invasion. To enhance our understanding of B. dorsalis' olfactory behavior and explore potential strategies for behavior control, we have reviewed recent literature on its olfactory plasticity and potential molecular mechanisms.

Reproductive behavior of fruit flies: courtship, mating, and oviposition

Many species of the Tephritidae family are invasive and cause huge damage to agriculture and horticulture, owing to their reproductive characteristics. In this review, we have summarized the existing studies on the reproductive behavior of Tephritidae, particularly those regarding the genes and external factors that are associated with courtship, mating, and oviposition. Furthermore, we outline the issues that still need to be addressed in fruit fly reproduction research. The review highlights the implications for understanding the reproductive behavior of fruit flies and discusses methods for their integrated management and biological control. © 2023 Society of Chemical Industry.