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Research

Overview

Insects’ ability to sense and react to their environment contributes to the persistence of species. Chemosensation is not only instrumental in insects’ identification of food, mates, and predators, but olfaction in particular is influential to geographical distribution and overall survival. Insect endosymbionts have recently been shown to influence the plasticity of these insect olfactory systems, modifying insect behavior in response to volatile signals. Previous studies have unraveled mechanisms involved in the acquisition, maintenance, and transmission of endosymbionts, and other groups have studied effects of endosymbionts on insect reproduction. Yet, little is known about how endosymbionts directly affect transmissibility of insect-borne diseases through mating-independent mechanisms. Even less is known about which and how endosymbionts impact host-seeking behavior in insect vectors of disease. An investigation of the impact of endosymbionts on insect olfactory systems, particularly in harmful insect vectors of human diseases, is thus required. These findings may be useful in devising new, highly-targeted, environmentally-safe strategies for control of insect pests and/or the diseases they transmit.

Assess changes to the olfactory system in response to gut microbial community composition.

We hypothesize that specific endosymbionts, whether individually or in complex communities with other endosymbionts, can evoke changes to the olfactory system in insects. We validate this hypothesis first in the fruit fly D. melanogaster, which serves as an apt model organism for harmful insect pests and has been used successfully for studying host-microbe interactions. We will map the fluctuating endosymbiont community over time and in different regions of the fly. We will then create a germ-free (axenic) D. melanogaster system, with which we will reintroduce endosymbionts individually or in combination, to determine whether and which endosymbionts affect insect olfaction. This approach will reveal which endosymbionts are capable of changing olfactory-guided behavior.

Reveal endosymbiont-mediated mechanisms underlying changes to the host olfactory system.

We hypothesize that the modulation of olfactory-guided behaviors is caused by endosymbiont-induced changes in the expression levels of select receptors – ionotropic receptors (IRs) and odorant receptors (ORs) – which sense volatile signals. We will introduce our behavior-altering endosymbionts into each receptor mutant, and test for olfactory-guided behavior. We will observe which receptors, when removed or overexpressed, can restore the insect to baseline conditions, despite the presence of behavior-altering endosymbionts. This analysis will tell us which receptors are being differentially expressed because of these select endosymbionts. We will further probe the molecular mechanism underlying this endosymbiont-mediated olfactory system plasticity and map the signaling pathways by which these bacterial molecules regulate IR and OR expression. Altogether, we will understand how secreted molecules from endosymbionts affect their hosts’ genome.

Characterize endosymbionts present in Aedes albopictus.

To understand the impact of endosymbionts on insect vectors of disease, we will investigate the microbiome of the mosquito A. albopictus. We hypothesize that a similar effect of endosymbionts on insect host olfaction will be observed in vectors of disease, potentially through a conserved molecular mechanism. We first review existing A. albopictus microbiome profiles from population-wide and individual-level microbiome studies. We will compare existing data from strains harboring viral pathogens (e.g., West Nile virus, dengue virus), to newly-eclosed mosquitoes reared in our facility, which are uninfected. We will particularly focus on bacterial strains which are represented in insect data obtained from regions of high disease transmission. We will rear axenic mosquitoes, to which we will reintroduce endosymbionts either individually or in combination. We will then subject these mosquitoes to the olfactory behavioral assays to determine whether changes to the microbiome composition can alter olfactory-guided behaviors in mosquitoes, as well. After identifying communities of endosymbionts which effect behavioral changes in the host, we will engage in an investigation of the bacterial cell-cell communication which underlies their host behavior-modulation. We aim to reveal how particular complex communities lend themselves to improved insect host colonization, and even benefit transfer of endosymbionts or viral pathogens from insect hosts to their prey.