New preprint on bioRxiv
We’re excited to share a new paper on bioRxiv! In this study we discovered a bunch of cool new stuff about fly taste.
First, we wanted to know how sweet and bitter tastes influence a range of behaviors beyond feeding (which is most often studied). We optogenetically activated sweet- or bitter-sensing neurons and found that they drove opposing effects on locomotor patterns, spatial preference, and associative learning. The video shows an example where bitter neurons are activated whenever flies go to the upper left or lower right quadrants of the arena, so they navigate away from those areas.
Next, we examined how different subsets of bitter neurons, located in different organs, contribute to behavior. Flies have taste neurons in multiple organs such as the legs, proboscis, and pharynx, which are thought to control different aspects of behavior. Surprisingly, we found that neurons in any of those three organs elicited a broad and highly overlapping set of behaviors. These different bitter inputs are therefore likely to converge onto common downstream pathways.
To look at the downstream pathways, we used transsynaptic tracing to label neurons postsynaptic to each subset of bitter neurons. These experiments showed that different subsets of bitter neurons connect to overlapping pathways, but with biased connectivity (i.e. different subsets preferentially connect to different pathways).
Labeling of neurons that are postsynaptic to different types of bitter-sensing cells, termed “second-order” bitter neurons.
Finally, we characterized one specific type of second-order bitter neuron. We found that it receives input from multiple organs and regulates a subset of bitter-induced behaviors.
Together, these results suggest that different bitter inputs are selectively integrated early in the taste circuit, thus pooling bitter information across the body, and they drive an overlapping set of behaviors. At the same time, the circuit diverges into multiple pathways that may have different behavioral roles.
This work was conducted by Dr. Devineni and some fantastic mentees at Columbia: former technician Julia Deere (now a PhD student at Rockefeller), former technician Hannah Uttley, and former City College of New York undergraduate Nicole Martinez Santana (now a nursing student at Columbia). Congrats to all the authors!
If you have any interest in investigating what the rest of the taste circuit looks like (what the heck do all those other second-order neurons do? do their bitter responses vary? who do they connect to?), learn more about joining the lab here!
