Molecular genetic characterization of Drosophila reproductive behaviours for exploitation in insect population control

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 [1, 2]. Currently, we do not know what other receptors SP binds in the Drosophila brain and how the neuronal circuits are built to induce this behavioural switch.

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. To identify the neuronal circuitry underlying the sex-peptide response, we will use 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 [2].

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.

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