ODORANT RECEPTOR EXPRESSION DURING NEURONAL DEVELOPMENT IN THE MALARIA VECTOR ANOPHELES COLUZZII NGOUSSO
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The African mosquito Anopheles gambiae is an important vector of malaria, a blood-borne disease that affects millions around the world. The mosquito uses its sense of smell to identify and locate human hosts. An understanding of the vector’s olfactory system can lead to strategies to reduce transmission of the disease. Our lab discovered that Anopheles gambiae odorant receptor (AgOR) expression in developing mosquito olfactory neurons on the antenna might be amendable to transcriptional regulation, even at adult stages. A central aim of my thesis was to characterize the developmental expression pattern of AgORs during pupal stages, and the effect of odors on AgOR expression at adult stages. My thesis work focused on Anopheles gambiae odorant receptors AgOR 2, AgOR 11, and AgOR 24, which prior work showed might be particularly regulatable. During pupal stages, I discovered that while AgOR 2 and AgOR 11 gene expression increased closer to pupal eclosion, AgOR 24 gene expression decreased in the late-stage pupae. These data suggest that AgORs might have differential expression patterns throughout development, and not all odorant receptors are upregulated during eclosion. During adult stages, I discovered that prolonged exposure to 4-methylcyclohexanol (an oviposition attractant that activates antennal AgOR 11 receptors) during early adult stages led to a greater number of AgOR 11-positive neurons in comparison to exposure to a mineral oil control. This result suggests that in the presence of an activating odor, there is an increase in the number of neurons expressing an olfactory receptor that can respond to that odor. In terms of vector control, these data suggest that the olfactory neurons of mosquitoes might be able to adapt to its odor environment to influence odor-based behaviors such as host-seeking or oviposition.