Relevant Degree Programs
Most projects centre on the neural circuits underlying taste processing and feeding in the fly brain. Potential projects include looking at circuit mechanisms underlying taste integration, hunger, feeding, taste memories, chemosensory integration, and taste circuit development.
Complete these steps before you reach out to a faculty member!
- Familiarize yourself with program requirements. You want to learn as much as possible from the information available to you before you reach out to a faculty member. Be sure to visit the graduate degree program listing and program-specific websites.
- Check whether the program requires you to seek commitment from a supervisor prior to submitting an application. For some programs this is an essential step while others match successful applicants with faculty members within the first year of study. This is either indicated in the program profile under "Requirements" or on the program website.
- Identify specific faculty members who are conducting research in your specific area of interest.
- Establish that your research interests align with the faculty member’s research interests.
- Read up on the faculty members in the program and the research being conducted in the department.
- Familiarize yourself with their work, read their recent publications and past theses/dissertations that they supervised. Be certain that their research is indeed what you are hoping to study.
- Compose an error-free and grammatically correct email addressed to your specifically targeted faculty member, and remember to use their correct titles.
- Do not send non-specific, mass emails to everyone in the department hoping for a match.
- Address the faculty members by name. Your contact should be genuine rather than generic.
- Include a brief outline of your academic background, why you are interested in working with the faculty member, and what experience you could bring to the department. The supervision enquiry form guides you with targeted questions. Ensure to craft compelling answers to these questions.
- Highlight your achievements and why you are a top student. Faculty members receive dozens of requests from prospective students and you may have less than 30 seconds to pique someone’s interest.
- Demonstrate that you are familiar with their research:
- Convey the specific ways you are a good fit for the program.
- Convey the specific ways the program/lab/faculty member is a good fit for the research you are interested in/already conducting.
- Be enthusiastic, but don’t overdo it.
G+PS regularly provides virtual sessions that focus on admission requirements and procedures and tips how to improve your application.
Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Nov 2019)
To survive animals must find and consume nutritive foods. The chemical composition of food sources is evaluated using gustation. Because of its importance to survival, feeding behaviors are tightly regulated. Changes in feeding occur in response to the external environment and the animal’s internal physiological state. Expendable behaviours can be suppressed during starvation to prioritize feeding. This thesis examines the role of two factors in feeding decisions: the location of taste input and starvation. Pharyngeal sense organs in Drosophila are the last evaluation point before food is ingested. It was previously unclear whether they served a unique function in feeding. To investigate this, we focused on appetitive gustatory pharyngeal neurons and showed they express nine gustatory receptors which respond to sweet compounds. Mutants lacking peripheral taste have functional pharyngeal sense organs. In the absence of peripheral taste cues, the pharyngeal sense organs can drive the choice and ingestion of sweet compounds by sustaining consumption. Knocking down pharyngeal neurons in these mutants allowed us to examine a sweet-blind fly in a short term feeding assay. Putatively sweet-blind flies do not show a preference for sweet compounds in a short-term feeding assay, suggesting that nutrient sensing is not operating in this context. Starved flies have an increased tolerance for bitter foods, which is mediated by sensitization and desensitization of sweet and bitter taste, respectively. Mechanisms that cause the sensitization of sweet taste have been studied, but those that underlie desensitization of bitter taste were unknown. We identify a pair of octopaminergic/tyraminergic modulatory neurons called the ventrolateral cluster of octopaminergic neurons (OA-VLs). Because OA-VLs exist in close physical proximity to bitter neuron axon terminals but are not postsynaptic to them, we examined their function as modulators of bitter neuron output. Tonic firing rate of OA-VLs decreases as a function of starvation. Octopamine and tyramine are sufficient to potentiate bitter neuron response in starved flies, suggesting that reduction in OA-VL activity during starvation depotentiates bitter neuron output. Silencing OA-VLs causes a reduction in bitter neuron output and increased acceptance of bitter compounds. OA-VLs may act directly on bitter sensory neurons through the Oct-Tyr receptor.
Master's Student Supervision (2010 - 2018)
Although feeding behavior is a matter of life and death for animals, the genetic factors that control it remain poorly understood. We have identified a novel regulator of hunger-induced behavior through comparison of transcriptomic changes in the fruit fly Drosophila melanogaster and the yellow fever mosquito Aedes aegypti. Head mRNA from each insect was sequenced at a roughly equivalent level of starvation. Using data gleaned from the protein orthology database OrthoDB, we looked for gene pairs in which both A. aegypti and D. melanogaster orthologs were significantly regulated by starvation. This identified Juvenile Hormone esterase (Jhe) as a possible modulator of hunger-induced behavior. Pan-neuronal knockdown of Jhe resulted in increased food consumption and caused enhancement of starvation-induced sleep suppression in Drosophila. These behavioral phenotypes were not caused by a developmental or metabolic defects, and were reproduced by feeding adult Drosophila methoprene, a synthetic Juvenile Hormone analog. Application of precocene I, an inhibitor of Juvenile Hormone biosynthesis, reversed the phenotype. Our analysis suggests that Jhe (and Juvenile Hormone by extension) is a novel and biologically relevant regulator of hunger-induced behavior.
The sense of taste plays a critical role in animal behaviour. The ability to taste prior to ingestion allows an animal to differentiate between beneficial substances, such as calorie-rich foods, from those that may be toxic and which often taste bitter. For animals to avoid harmful substances, exposure to bitter substances must not only activate bitter-sensing neurons, but also suppress the response of acceptance-mediating neurons. The ability to choose appropriately between consumption and avoidance requires functional neuronal circuits in the brain that start with the processing of taste input from the environment and end with a behavioural output. γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the insect and mammalian brain. We show evidence of functional connections between GABAergic interneurons (those that release GABA) and taste sensory neurons in the fly brain. Neurons that detect palatable substances (i.e. sugars) express high levels of a metabotropic GABAB receptor (GABABR), whereas those that sense unpalatable substances (i.e. bitter compounds) express little to no GABABR. Using a behavioural assay (proboscis extension reflex) and calcium imaging, I investigated how GABAergic inhibition shapes sweet neuron output and contributes to the integration of competitive taste stimuli. When GABABR is knocked down in sugar neurons, the behavioural response to sugars is elevated. Pharmacological assays show that GABAergic activation suppresses the sweet neuron response while GABAergic blockade potentiates the response. In flies expressing GABABR knockdown, suppression of sugar neuron activity by bitter exposure is relieved both behaviourally, by increased acceptance of bitter mixtures, and cellularly, by increased calcium response. Our model proposes that GABA acts via GABABR in the fly taste circuit to produce ecologically relevant responses to both attractive and repellent energy sources.