Drosophila Chemoreception and Threats of the Anthropocene

Date of Award

Spring 2022

Document Type


Degree Name

Doctor of Philosophy (PhD)


Molecular, Cellular, and Developmental Biology

First Advisor

Carlson, John


The term ‘odorant-binding proteins (Obps)’ is used to refer to a large family of insect proteins that are exceptional in their number, abundance and diversity. The name derives from the expression of many family members in the olfactory system of insects and their ability to bind odorants in vitro. However, an increasing body of evidence reveals a much broader role for this family of proteins. Recent results also provoke interesting questions about their mechanisms of action, both within and outside the olfactory system. Here we describe the identification of the first Obps and some cardinal properties of these proteins. We then consider their function, discussing both the prevailing orthodoxy and the increasing grounds for heterodox views. We then examine these proteins from a broader perspective and consider some intriguing questions in need of answers. Odorant binding proteins (Obps) are expressed at extremely high levels in the antennae of insects, and have long been believed essential for carrying hydrophobic odorants to odor receptors. Previously we found that when one functional type of olfactory sensillum in Drosophila was depleted of its sole abundant Obp, it retained a robust olfactory response (Larter et al., 2016). Here we have deleted all the Obp genes that are abundantly expressed in the antennal basiconic sensilla. All of six tested sensillum types responded robustly to odors of widely diverse chemical or temporal structure. One mutant gave a greater physiological and behavioral response to an odorant that affects oviposition. Our results support a model in which many sensilla can respond to odorants in the absence of Obps, and many Obps are not essential for olfactory response, but that some Obps can modulate olfactory physiology and the behavior that it drives. The Anthropocene era poses a critical challenge for all organisms: they must cope with new threats at a faster rate than ever before. These threats include toxic chemical compounds released into the environment by human activities. Here, we examine high concentrations of heavy metal ions as an example of anthropogenic stressors. We find that different subsets of taste receptors contribute to avoidance behaviors towards nine metal ions when present at high concentrations that flies experienced rarely if ever until the Anthropocene. We analyze feeding and oviposition avoidance behaviors, and we identify taste organs, neurons, and receptors that contribute to the avoidance of metals. We find that metals activate some taste neurons and inhibit others. Receptor mutations have different effects on different avoidance behaviors. Some responses to metals are conserved across diverse dipteran species. Our results suggest mechanisms that may be essential to insects as they face challenges from environmental changes in the Anthropocene.

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