BRC-BIO: Amino acid taste coding mechanisms and modulation in D. melanogaster

All animals must continually make important dietary choices that impact health, reproduction, and survival. The nervous system plays a key role in directing feeding behavior through the sense of taste, where specialized sensory cells detect chemicals in food and activate neural circuits that encourage animals to avoid potential toxins and consume beneficial nutrients.

Taste loss is a common symptom of COVID-19 infection, and the recent pandemic highlighted the negative consequences of losing this chemical sense. However, many questions remain about how information about taste is encoded in the nervous system, even in normal conditions. Protein intake is essential in many animals, from humans to fruit flies, but protein needs change in response to internal factors such as diet and reproduction.

Amino acids, the building blocks of protein, are detected by taste cells, but it is unclear whether sensitivity to amino acid taste changes based on an animal’s internal physiology. The research in this proposal will utilize the fruit fly, Drosophila melanogaster, to describe the genes, cells, and neural circuits responsible for amino acid taste, and determine if amino acid taste sensitivity is influenced by factors such as hunger and diet.

By combining powerful genetic tools with simple behavioral assays, a diverse group of undergraduate students will contribute to this research through two courses and paid summer research experiences. Additional students will share scientific results and student narratives through Science Communication Internships. Overall, this project will help broaden the STEM workforce by providing accessible educational opportunities that build practical skills.

The sense of taste is often depicted as one cell type tuned precisely to one class of chemicals with one receptor. However, it is becoming clear from research in both Drosophila and mammals that gustation is not that simple: one tastant may activate multiple cell types or a single cell may express multiple receptors and detect many chemicals. Previously, the PI and others completed a detailed map of every taste cell across the Drosophila labellum (‘tongue’), and preliminary data using in vivo calcium imaging to quantify taste cell activation revealed that at least one cell type is strongly activated by amino acids.

In addition, stimulating the labellum with an amino acid mix led to a consistent proboscis extension response (PER), a simple feeding behavior that quantifies taste sensitivity. The overall hypothesis of this proposal is that amino acids activate at least two classes of taste cells to drive flexible, taste-induced feeding behaviors that can change based on internal needs.

The first aim will identify physiological factors that modulate the amino acid PER, while the second aim will uncover the full repertoire of cells and receptors necessary for amino acid detection combining calcium imaging and PER. The third aim will use connectomics to identify neural circuits of amino acid taste and determine if taste cell activation is modulated in response to protein needs.

This research combines cutting-edge neurobiology tools with behavioral assays to ultimately uncover how taste circuits are modified at a cellular level to lead to flexible dietary choices.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.