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Molecular and functional characterization of the odorant receptor2 (OR2) in the tiger mosquito Aedes albopictus.

Scialò F, Hansson BS, Giordano E, Polito CL, Digilio FA - PLoS ONE (2012)

Bottom Line: Our data indicate that AalOR2 is narrowly tuned to indole, and inhibited by (-)-menthone.In agreement with this results, these two compounds elicit two opposite effects on the olfactory-based behavior of A. albopictus larvae, as determined through a larval behavioral assay.In summary, this work has led to the cloning and de-orphaning of the first Odorant Receptor in the tiger mosquito A. albopictus.

View Article: PubMed Central - PubMed

Affiliation: Institute of Genetics and Biophysics A. Buzzati-Traverso, CNR, Naples, Italy.

ABSTRACT
In mosquitoes, the olfactory system plays a crucial role in many types of behavior, including nectar feeding, host preference selection and oviposition. Aedes albopictus, known also as the tiger mosquito, is an anthropophilic species, which in the last few years, due to its strong ecological plasticity, has spread throughout the world. Although long considered only a secondary vector of viruses, the potential of its vector capacity may constitute a threat to public health. Based on the idea that an improved understanding of the olfactory system of mosquitoes may assist in the development of control methods that interfere with their behavior, we have undertaken a study aimed at characterizing the A. albopictus Odorant Receptors. Here we report the identification, cloning and functional characterization of the AalOR2 ortholog, that represents the first candidate member of the odorant receptor (OR) family of proteins from A. albopictus. AalOR2 is expressed in the larval heads and antennae of adults. Our data indicate that A. albopictus OR2 (AalOR2) shares a high degree of identity with other mosquito OR2 orthologs characterized to date, confirming that OR2 is one of the most conserved mosquito ORs. Our data indicate that AalOR2 is narrowly tuned to indole, and inhibited by (-)-menthone. In agreement with this results, these two compounds elicit two opposite effects on the olfactory-based behavior of A. albopictus larvae, as determined through a larval behavioral assay. In summary, this work has led to the cloning and de-orphaning of the first Odorant Receptor in the tiger mosquito A. albopictus. In future control strategies this receptor may be used as a potential molecular target.

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Inhibitory effect of (–)Menthone on the AalOR2-“empty-neuron”.Representative trace of Single-Sensillum Recordings from AalOR2-ORCo in the ab3A ORN, in response to 10−3 M (–)-Menthone. The firing rates clearly indicate a decrease in the number of large spikes corresponding to the ab3A neuron in one second of activity. Like with the other odors, the experiments were carried out testing three independent UAST insertions and identical results were observed in all the lines. Three sensilla were analyzed per fly, for a total of three flies per each transgenic strain.
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pone-0036538-g006: Inhibitory effect of (–)Menthone on the AalOR2-“empty-neuron”.Representative trace of Single-Sensillum Recordings from AalOR2-ORCo in the ab3A ORN, in response to 10−3 M (–)-Menthone. The firing rates clearly indicate a decrease in the number of large spikes corresponding to the ab3A neuron in one second of activity. Like with the other odors, the experiments were carried out testing three independent UAST insertions and identical results were observed in all the lines. Three sensilla were analyzed per fly, for a total of three flies per each transgenic strain.

Mentions: To be certain that the endogenous odorant receptor in the empty neuron of our transgenic flies was lacking, we used ethyl butyrate [25], that elicits a strong excitatory response from the ab3A neuron only in the presence of OR22a. As expected, this chemical failed to elicit a response (data not shown). In order to obtain a direct indication of the response magnitude and kinetics, we generated peri-stimulus time histograms reporting the firing frequencies of AalOR2 as a function of time (Fig. 4). Firing rates were quantified by the number of spikes elicited in one second after stimulation compared to the spontaneous activity of the neuron (Fig. 5). We found that at a 10−3 M concentration, indole elicited the strongest response from AalOR2, inducing more than 130 spikes/sec. Moreover, as already reported for the in vitro assay, AalOR2 responded to several aromatic compounds such as each of the methylindoles and methylphenol. Most of the other odorants tested in our experiments elicited virtually no responses from AalOR2 (Fig. 5). Interestingly, when we used synthetic (–)-menthone (2S, 5R-trans-2-isopropyl-5-methylcyclohexanone), down to a 10−3 M concentration, we observed a strong inhibition of neuronal activity (Fig. 6).


Molecular and functional characterization of the odorant receptor2 (OR2) in the tiger mosquito Aedes albopictus.

Scialò F, Hansson BS, Giordano E, Polito CL, Digilio FA - PLoS ONE (2012)

Inhibitory effect of (–)Menthone on the AalOR2-“empty-neuron”.Representative trace of Single-Sensillum Recordings from AalOR2-ORCo in the ab3A ORN, in response to 10−3 M (–)-Menthone. The firing rates clearly indicate a decrease in the number of large spikes corresponding to the ab3A neuron in one second of activity. Like with the other odors, the experiments were carried out testing three independent UAST insertions and identical results were observed in all the lines. Three sensilla were analyzed per fly, for a total of three flies per each transgenic strain.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351472&req=5

pone-0036538-g006: Inhibitory effect of (–)Menthone on the AalOR2-“empty-neuron”.Representative trace of Single-Sensillum Recordings from AalOR2-ORCo in the ab3A ORN, in response to 10−3 M (–)-Menthone. The firing rates clearly indicate a decrease in the number of large spikes corresponding to the ab3A neuron in one second of activity. Like with the other odors, the experiments were carried out testing three independent UAST insertions and identical results were observed in all the lines. Three sensilla were analyzed per fly, for a total of three flies per each transgenic strain.
Mentions: To be certain that the endogenous odorant receptor in the empty neuron of our transgenic flies was lacking, we used ethyl butyrate [25], that elicits a strong excitatory response from the ab3A neuron only in the presence of OR22a. As expected, this chemical failed to elicit a response (data not shown). In order to obtain a direct indication of the response magnitude and kinetics, we generated peri-stimulus time histograms reporting the firing frequencies of AalOR2 as a function of time (Fig. 4). Firing rates were quantified by the number of spikes elicited in one second after stimulation compared to the spontaneous activity of the neuron (Fig. 5). We found that at a 10−3 M concentration, indole elicited the strongest response from AalOR2, inducing more than 130 spikes/sec. Moreover, as already reported for the in vitro assay, AalOR2 responded to several aromatic compounds such as each of the methylindoles and methylphenol. Most of the other odorants tested in our experiments elicited virtually no responses from AalOR2 (Fig. 5). Interestingly, when we used synthetic (–)-menthone (2S, 5R-trans-2-isopropyl-5-methylcyclohexanone), down to a 10−3 M concentration, we observed a strong inhibition of neuronal activity (Fig. 6).

Bottom Line: Our data indicate that AalOR2 is narrowly tuned to indole, and inhibited by (-)-menthone.In agreement with this results, these two compounds elicit two opposite effects on the olfactory-based behavior of A. albopictus larvae, as determined through a larval behavioral assay.In summary, this work has led to the cloning and de-orphaning of the first Odorant Receptor in the tiger mosquito A. albopictus.

View Article: PubMed Central - PubMed

Affiliation: Institute of Genetics and Biophysics A. Buzzati-Traverso, CNR, Naples, Italy.

ABSTRACT
In mosquitoes, the olfactory system plays a crucial role in many types of behavior, including nectar feeding, host preference selection and oviposition. Aedes albopictus, known also as the tiger mosquito, is an anthropophilic species, which in the last few years, due to its strong ecological plasticity, has spread throughout the world. Although long considered only a secondary vector of viruses, the potential of its vector capacity may constitute a threat to public health. Based on the idea that an improved understanding of the olfactory system of mosquitoes may assist in the development of control methods that interfere with their behavior, we have undertaken a study aimed at characterizing the A. albopictus Odorant Receptors. Here we report the identification, cloning and functional characterization of the AalOR2 ortholog, that represents the first candidate member of the odorant receptor (OR) family of proteins from A. albopictus. AalOR2 is expressed in the larval heads and antennae of adults. Our data indicate that A. albopictus OR2 (AalOR2) shares a high degree of identity with other mosquito OR2 orthologs characterized to date, confirming that OR2 is one of the most conserved mosquito ORs. Our data indicate that AalOR2 is narrowly tuned to indole, and inhibited by (-)-menthone. In agreement with this results, these two compounds elicit two opposite effects on the olfactory-based behavior of A. albopictus larvae, as determined through a larval behavioral assay. In summary, this work has led to the cloning and de-orphaning of the first Odorant Receptor in the tiger mosquito A. albopictus. In future control strategies this receptor may be used as a potential molecular target.

Show MeSH
Related in: MedlinePlus