Chemosensory enzymes in sex pheromone communication: an integrative study in the fruit fly – CHEMSENZ

We will characterize the enzymes putatively involved in the inactivation of two pheromone from drosophila. The candidate enzymes will be identified by molecular approaches. Using genetic tools, we will then inhibit the expression of these enzymes and we will study the effect of this inhibition on the neuron responses to the pheromones and on the sexual and social behaviours of the flies. At the biochemical level, we will produce recombinant enzymes to test their kinetic properties.

Too early

Our results would allow to better understand the functionning of insect olfactory and gustatory systems, and in particular the step of signal inactivation. If the chemosensory enzymes are required for an appropriate response of insects to odorant and tastant molecules, then it will be possible to develop specific inhibitors in order to disturd pest insect behaviours.

Too early

Insect pests cause enormous harm to human health and agriculture. Intensive researches are currently conduced to develop new strategies for their control, based on recent progress in the molecular and cellular biology of insect chemoreception. Despite large progress in the understanding of the molecular basis of insect olfaction and taste, the step of signal inactivation is still largely unknown, although this inactivation step is essential in the dynamic of chemoreception, participating in the olfactory and gustatory sensitivities. Preliminary studies suggest that enzymatic degradation of odorants occurs in the vicinity of the olfactory receptor neurons. Rapid metabolism of signal molecules should allow controlling the concentration of these compounds in the sensory organs thus preventing the continuous stimulation of receptors. This hypothesis has been postulated for two decades but has never been demonstrated, neither in insects nor in vertebrates. The purpose of the present project is to verify this hypothesis with the fruit fly Drosophila melanogaster. We will take advantage of the well defined pheromonal system of this model insect, which involves both odorant and tastant compounds. We aim at identifying new molecular components that specifically degrade these compounds, as a paradigm to be generalized to pest insects. We are convinced that these chemosensory enzyme genes of represent potential targets for pest insect control.
This project will focus on two D. melanogaster sex pheromones, 7-Tricosene (7-T) and 11-cis-vaccenyl acetate (cVA) as model substrates. These pheromones are detected by different sensory modalities, taste for 7-T and olfaction for cVA, but both strongly inhibit male courtship. The perception of these two pheromones has been deeply investigated: 1) the sensory receptors and binding-proteins involved in their reception are identified; 2), the responsive sensilla are precisely mapped on the olfactory/taste organs, allowing genetic targeting of candidate chemosensory enzymes in these sensilla; 3) electrophysiological and behavioural responses of males to these pheromone stimuli are well documented; 4) synthetic compounds are available for the tests. Candidate chemosensory enzymes involved in the degradation of these two pheromones will be identified both in silico with the well annotated genome of the fruit fly, together with transcriptomic approaches.
The great advantage of the Drosophila model is to test the participation of such enzymes in signal termination by the manipulation of the corresponding genes in vivo. The functional effects induced by genetic manipulation will be monitored both on the neuronal responses and on the sexual behaviour. We will then only focus on the enzymes whose inhibition induces significant phenotype in vivo to produce the corresponding recombinant enzymes.Their interaction with sex pheromones will be qualitatively (substrate confirmation) and quantitatively (affinity, efficiency) analyzed to establish a link between their catalytic properties to 7-T/cVA and their in vivo effects.
All these experimental approaches should converge to provide us, for the first time, a holistic picture of the mechanisms involved in signal inactivation in animal chemosensory systems.