Molecular and functional characterization of the Odorant Receptor2 (OR2) in the tiger mosquito Aedes albopictus.

In mosquitoes, olfactory system plays a crucial role in many behaviors, including nectar feeding, host preference selection, searching for the right place to lay eggs. A.albopicus, known also as tiger mosquito, is an anthropophilic species which in the last years, due to a strong ecological plasticity, has spread throughout the world and all over Italy with a high abundance in man-made environments. Although long considered a secondary vector of viruses, the potentiality of its vectorial capacity is very dangerous and may constitute the foundation for a public health alert. Nevertheless, to date, for this mosquito nothing is known at molecular level. Based on the idea that an improved understanding of the olfactory system of mosquitoes may help in developing control methods that interfere with its behavior, recently we have undertaken a study aimed to characterize the A. albopictus Odorant Receptors. During my PhD work, I focused my attention on the identification, cloning and functional characterization of the A. albopictus OR2 ortholog. My data indicate that A. albopictus OR2 (AalOR2) shares a high degree of identity with the other mosquito OR2 orthologs characterized to date, confirming that OR2 is one of the most conserved mosquito ORs; furthermore, AalOR2 is expressed in the olfactory appendages of larvae and adults and its expression increases after a blood meal, as determined by a semi-quantitative RT-PCR. Interestingly, this is the first report of an up-regulation of an OR in response to a blood meal; this increase could suggest a role of AalOR2 in searching oviposition right places. AalOR2, such as the other orthologs, is narrowly tuned to indole, a ubiquitous volatile compound that has been linked to host seeking, and oviposition. The de-orphaning of AalOR2 has been obtained, with same results, through Ca2+ imaging assay in HEK293 cells, and “in vivo” experiments using the Single Sensillum Recording (SSR) in an engineered neuron of the fruitfly Drosophila melanogaster that express AalOR2. Furthermore, by using this technique, I was able to identify also a molecule, (-)Menthone, that produced an inhibitory effect on this Odorant Receptor. In summary, this work led to the cloning and de-orphaning of the first Odorant Receptor in A. albopictus, that may be used as potential molecular target for developing environmentally friendly strategies to control mosquito populations.