Interdisciplinary doctorat in Chemical Ecology – Neurobiology, molecular biology, behavioral ecology, evolutionary biology
November 2025-2028
Thesis title
Contribution of peripheral olfactory mechanisms to the evolution of male attraction behaviors in Tephritidae
Direction
- Emmanuelle Jacquin-Joly, DR INRAE, iEES-Paris, Versailles
- Vincent Jacob, chercheur CIRAD, UMR PVBMT, Saint-Pierre, La Réunion
Associates
- Institute of Ecology and Environmental Sciences of Paris (IEES-Paris), INRAE, Paris, Versailles
- Peuplement végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT), CIRAD, Saint-Pierre, Réunion
- Agriodor, French Start-up in insect biocontrol through odors, Rennes
Scientific background of the thesis
The agroecological transition toward durable, environmentally friendly agriculture requires developing methods to control crop pests as an alternative to using pesticides. Several of these methods rely on insect olfactory behavior disruption, for instance using attractive odors that mimic natural chemical interactions between insects and their environments, and that can be used for the efficient and specific trapping of pests with minimal impact on non-target insects.
Identifying behaviorally active odorants requires a good understanding of the chemical ecology of the targeted species. An innovative approach, the so-called reverse chemical ecology approach, proposes to accelerate their discovery by focusing on the molecular mechanisms of insect olfaction, and in particular the odorant receptors. Insect odorant receptors belong to an atypical family of proteins whose three-dimensional structure has just been revealed (Butterwick et al., 2018; Y. Wang et al., 2024; Zhao et al., 2024). This paves the way for predicting potential agonists in silico through new modeling approaches (Comte et al., 2025). This PhD project aims to apply these techniques to identify new male attractants for Tephritidae fruit flies, which includes major fruit and vegetable pests worldwide (e.g., the Oriental fruit fly, Bactrocera dorsalis; the melon fly, Zeugodacus cucurbitae; and the Mediterranean fruit fly, Ceratitis capitata), and for which we already identified the odorant receptor repertoires (Persyn et al., 2025). The identification of new male attractants could eventually become one of the first concrete applications of these techniques in crop protection. Furthermore, a comparative approach across different species will help decipher the evolutionary history of an unusual interaction between plants (that emit the attractants) and insects (males use these compounds to seduce females), which will help understanding the potential for olfactory adaptation in insects and the interdependence between intraspecific and interspecific communication.
Thesis objectives
The first part of this project will focus on an already identified odorant receptor tuned to methyleugenol, one of the most potent attractants to trap males from the oriental fruit fly, B. dorsalis, but whose use is restricted due to its carcinogenicity. Working at the receptor level, the aim will be to identify alternative agonists to methyleugenol able to induce the same functional and behavioral responses in male Oriental fruit flies as this potent attractant. A non-toxic, alternative attractant could be used to mass trap the pest in fruit orchards. The work will also investigate the occurrence of another receptor to methyleugenol, that is suspected to exist in B. dorsalis.
The second part of this thesis will consist in comparing the functional properties of orthologous receptors across several Tephritidae species, notably those present in La Réunion. This objective, more fundamental, will be to test the hypothesis that receptor sensitivity to male attractants has been reshaped throughout the evolution history of Tephritidae under the influence of ecological constraints specific to each species.
Methodology
- Genetic approaches, based on the heterologous expression of olfactory receptors in the olfactory system of Drosophila.
- Electrophysiological approaches, including single-sensillum recordings of olfactory neuron activity.
- Modeling approaches: predicting odorant receptor 3D structure and new ligands in silico, in collaboration with partner laboratories.
- Behavioral ecology approaches using automated videotracking of insect trajectories in response to olfactory stimulation.
Scientific and technical environment
The student will work alternatively in two laboratories that will jointly supervise the thesis.
- At IEES-Paris, INRAE, Versailles, France, the student will have access to facilities and resources for genetic manipulation of Drosophila, electrophysiological recordings, and molecular phylogeny of insect olfactory receptors.
- At PVBMT, Saint-Pierre, Ile de la Réunion, the student will have access to an insect rearing facility with eight species of Tephritidae of agroeconomic interest, and will benefit from facilities and resources for electrophysiology and behavioral tests.
- The student will enroll in the “Science, Technology and Health” doctoral program at the University of Réunion, which focuses on the biodiversity of tropical eco-agro-systems.
Profile and desired skills
The ideal candidate will have a Master’s degree in Biology or Ecology and a solid foundation in one of these fields. He or she will also have knowledge in Chemical Ecology, Insect Behavior, Genetics Electrophysiology, and/or data processing (statistical analysis).
Terms and conditions of application
Candidates must submit a resume + cover letter + one or two reference letters to :
Emmanuelle Jacquin-Joly : emmanuelle.joly@inrae.fr
Vincent Jacob : vincent.jacob@cirad.fr
Before October 1st
Other information
We are looking for a highly motivated candidate to study insect behavior and its physiological and molecular corelates. The student will have the opportunity to conduct part of their thesis research on Reunion Island, a tropical island, so adaptability is essential.
References
- Butterwick, J. A., del Mármol, J., Kim, K. H., Kahlson, M. A., Rogow, J. A., Walz, T., & Ruta, V. (2018). Cryo-EM structure of the insect olfactory receptor Orco. Nature, 560(7719), 447–452. https://doi.org/10.1038/s41586-018-0420-8
- Comte, A., Lalis, M, Brajon L., Moracci R., Montagné N., Topin J., Jacquin-Joly E. E., Fiorucci S. (2025) Accelerating ligand discovery for insect odorant receptors. Int. J. Biol. Sci. 21(5):2101-2117 http://dx.doi.org/10.7150/ijbs.105648
- Persyn E, Duyck, P-F, François M-C, Mille C, Jacob V and Jacquin-Joly E (2025) Transcriptomic analyses in thirteen Tephritidae species provide insights into the ecological driving force behind odorant receptor evolution. Molecular Phylogenetics and Evolution, 206:108322, 14 p. https://doi.org/10.1016/j.ympev.2025.108322
- Wang, Y., Qiu, L., Wang, B., Guan, Z., Dong, Z., Zhang, J., Cao, S., Yang, L., Wang, B., Gong, Z., Zhang, L., Ma, W., Liu, Z., Zhang, D., Wang, G., & Yin, P. (2024). Structural basis for odorant recognition of the insect odorant receptor OR-Orco heterocomplex. Science (New York, N.Y.), 384(6703), 1453–1460. https://doi.org/10.1126/science.adn6881
- Zhao, J., Chen, A. Q., Ryu, J., & Del Mármol, J. (2024). Structural basis of odor sensing by insect heteromeric odorant receptors. Science, 384, 1460–1467. https://doi.org/10.1126/science.adn6384
