• Identify the wiring diagram of the Tap Gustatory Circuit (TGC).
In Drosophila, a mini circuit of sweet perception has been recently identified. For other modalities, almost all the projection and regulatory neurons are unknown. Tap positive cells have been confirmed to overlap with subsets of sweet and bitter sensory neurons, as well as a few previously undescribed gustatory sensory neurons. Therefore, firstly I am examining which taste stimuli these Tap+ neurons respond to, aiming to investigate the external trigger of the TGC. Additionally, I identified Tap positive neurons in novel cell populations within the region where known gustatory regulatory, and putative projection neurons arborize. Thus, I am studying whether these sensory, regulatory and projection neurons directly communicate with each other, responding to similar taste stimuli, to form an entire neuronal circuit.
• Define the relationship between TGC activity, feeding behaviour and energy homeostasis.
The gustatory network assembles and exchanges information according to internal and external status to direct a behavioural decision. However, it is not clear how gustatory neuronal circuit responds to energy stasis. I am characterizing neuronal activity, behaviour and metabolism in holistic multi-modal approach. Specifically, the correlation among TGC, food intake, body weight, fly rhythm and activity are investigated to reveal the strategy of the animals in responding to both external and internal changes.
• Characterize Tap function within the TGC.
In parallel with the previous aim, I will study the function of Tap in the TGC. I found that Tap expression changes in the gustatory regulatory neurons upon starvation, suggesting that Tap levels are regulated by internal satiety state. I will study Tap function in regulating energy stasis to circuit activity to help generate state-appropriate behaviours. Thus, Tap function will be characterized by gain and loss of function approaches to uncover the molecular mechanism of such correlations.
These three aims are carried out in parallel, and each has the potential to create novel insight into the gustatory biology. More importantly, the combination of these three aims will shed the light on the relationship between neuronal circuit anatomy, activity, molecular features and animal behaviour.
