Abstract
Odorant degrading enzymes (ODEs) are thought to be responsible, at least in part, for olfactory signal termination in the chemosensory system by rapid degradation of odorants in the vicinity of the receptors. A carboxylesterase, specifically expressed in Drosophila antennae, called “juvenile hormone esterase duplication (JHEdup)” has been previously reported to hydrolyse different fruit esters in vitro. Here we functionally characterize JHEdup in vivo. We show that the jhedup gene is highly expressed in large basiconic sensilla that have been reported to detect several food esters. An electrophysiological analysis demonstrates that ab1A olfactory neurons of jhedup mutant flies exhibit an increased response to certain food acetates. Furthermore, mutant flies show a higher sensitivity towards the same odorants in behavioural assays. A phylogenetic analysis reveals that jhedup arose as a duplication of the juvenile hormone esterase gene during the evolution of Diptera, most likely in the ancestor of Schizophora, and has been conserved in all the 12 sequenced Drosophila species. Jhedup exhibits also an olfactory-predominant expression pattern in other Drosophila species. Our results support the implication of JHEdup in the degradation of food odorants in D. melanogaster and propose a neofunctionalization of this enzyme as a bona fide ODE in Drosophilids.
Highlights
The candidate ODEs identified to date belong to various detoxification enzyme families, including cytochrome P450s (CYPs), aldehyde oxidases (AOXs) and carboxylesterases (CCEs)[18,19,20]
In toto observations of flies expressing green fluorescent protein (GFP) under the control of the jhedup promotor showed a strong labelling of the 3rd antennal segments and maxillary palps, confirming an olfactory-restricted expression of jhedup (Fig. 1b)
Our results showed that jhedup is highly and broadly expressed in the third antennal segment, in the area of the large basiconic sensilla and that it is at least associated with non-neuronal cells from ab[1] and ab[3] sensilla, either accessory cells surrounding the ORNs or epidermal cells
Summary
The candidate ODEs identified to date belong to various detoxification enzyme families, including cytochrome P450s (CYPs), aldehyde oxidases (AOXs) and carboxylesterases (CCEs)[18,19,20]. The fatty acid desaturase Desat[1] has been shown to play a role in sex pheromone discrimination of fruit flies[32] while the P450 CYP6a20 seems involved in the regulation of aggressiveness[33], but for both enzymes the actual substrates remain unknown, including their role in antennal functioning. In contrast the role of the CCE esterase 6 (Est6) has been described in more detail and has been shown to be involved in the physiological and behavioural responses to the Drosophila sex pheromone cVA and to ubiquitous acetates emitted by food sources[34,35]. In order to clarify the function of jhedup in D. melanogaster, we investigated its precise expression pattern in olfactory tissues using qPCR and fluorescent labelling, as well as its role in the detection of various food acetate esters applying electrophysiological and behavioural approaches on a mutant strain. We analysed the phylogenetic relationship of jhe and jhedup within the Diptera, in order to determine when it arose for the first time during insect evolution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
