Primary Supervisor: Dr Matthias Soller, School of Biosciences
Secondary supervisor: Carolina Rezaval
PhD project title: Molecular genetic characterization of Drosophila reproductive behaviours for exploitation in insect population control
University of Registration: University of Birmingham
Female reproductive behaviours in most insects profoundly change after mating leading to rejection of courting males and induction of egg laying. Furthermore, many insects only mate once. Thus interfering with reproductive behaviours offers novel and yet little explored routes for pest-management.
Since reproductive behaviours and their regulation are most fundamental to all animals, they are hard-wired into the brain making them amenable to molecular and cellular characterization by genetic manipulation. In Drosophila, the key molecule inducing these post-mating behaviours (PMRs), is male-derived sex-peptide (SP) transferred during mating together with sperm. SP induced PMRs can last up to one week. Our recent research suggests that SP enters the brain by binding to a recently characterized G-protein coupled receptor, SPR . Currently, we do not know what other receptors SP binds in the Drosophila brain and have only a fragmentary understanding how the neuronal circuits are built to induce this behavioural switch [2, 3].
Our recent studies showed that there are several distinct neuronal populations that can via exposure to SP induce refusal to remate and egg laying. Although we do not know where in the fly these neurons are located, we could show that these two post-mating responses can be separated. The aim of this project will be to identify the neuronal circuitry underlying the sex-peptide response. To map this circuitry we will be using splitGAL4 gene expression intersection of enhancer fragment lines of known genes inducing the SP response (e.g. ppk, dsx and fru) to deliver membrane-tethered SP to only few neurons to identify the response initiating neurons. We will then apply trans-synaptic labelling in the context of the FLY Connectome to identify secondary neurons. These neurons will then be further characterized by light induced manipulation of neuronal properties in specific parts of the female fly body. Such optogenetic manipulation has the advantage to be fully controllable in space and time. With these experiments we will test the hypothesis that the response to SP is comprised of a modular assembly of individual elements, e.g. refusal to remate or induction of egg laying. Compared to the previous model arguing for central induction of all PMRs, a modular assembly of individual PMRs holds evolutionary flexibility during speciation and adaptation to diverse habitats, but can maintain basic regulatory principles such as the control of egg laying. Complementary to the molecular and cellular characterization of the sex-peptide response, we will employ pharmacological interrogation of this pathway .
We anticipate that the knowledge obtained from our studies will be applicable to a wide range of pest insects pinpointing towards novel strategies for pest management to protect crop and control insect-born diseases by interfering with egg laying. In particular, our findings are directly transferable to the close relative Drosophila suzukii, one of the few species able to lay eggs into ripening fruits. D. suzukii is currently invading Europe including the UK and causing damage worth billions of pounds to fruit production.
- Nallasivan, M.P., Haussmann, I.U., Civetta, A. and Soller, M. (2021) Channel nuclear pore protein 54 directs sexual differentiation and neuronal wiring for female reproductive behaviors in Drosophila. BMC Biology, in press.
- Haussmann , I.U., Hemani, Y., Wjiesekera, T., Dauwalder, B. and Soller, M. (2013) Multiple pathways mediate the sex-peptide-regulated switch in female Drosophila reproductive behaviours. Proc. R. Soc. B, 280: 20131938.
- Soller, M., Haussmann, I.U., Hollmann, M., Choffat, Y., White, K., Kubli, E. and Schafer, M.A. (2006). Sex-peptide-regulated female sexual behavior requires a subset of ascending ventral nerve cord neurons. Curr. Biol. 16: 1771-1782.
- Audsley and Down (2015) G protein coupled receptors as targts for next generation pesticides. Insect Biochem Mol Biol. S0965-1748(15)30030-8.
BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Animal Health and Welfare & Plant and Crop Science & Understanding the Rules of Life: Neuroscience and behaviour
Techniques that will be undertaken during the project:
- Drosophila genetics and behavior, transgenesis and CRISPR/Cas9 mutagensis
- Molecular Biology techniques including cloning and DNA recombineering, mRNA and protein expression analysis, cell culture, recombinant protein technology
- Imaging techniques including confocal Microscopy
Contact: Dr Matthias Soller, University of Birmingham