Chih-ying Su

Research

The sense of smell is one of the most intriguing senses: animals detect and discriminate an almost limitless number of odors in order to find food and mates while avoiding predators. Our research is focused on addressing how olfactory receptor neurons (ORNs) process odor information because these neurons are the primary source of sensory input. We are especially interested in how compartmentalization allows insect ORNs to process information through ephaptic interaction. We also investigate how neuromodulation can act on ORNs to regulate responses and influence odor-guided behaviors in Drosophila.

To understand the functional significance of ORN compartmentalization, we recently developed a new recording paradigm to demonstrate that ephaptic interaction is sufficient to mediate lateral inhibition between ORNs housed in the same sensillum ( Zhang et al., 2019). This unconventional lateral inhibition has a profound impact on neuronal spike activity and can thus regulate information processing at the earliest stages of olfactory coding. Furthermore, combining electrophysiology with a novel method that permits high-quality ultrastructural preservation for 3D electron microscopy of genetically labeled tissues ( Tsang et al, 2018), we found that lateral inhibition is predominantly asymmetric between compartmentalized ORNs, and that this feature arises from the size difference between the neurons ( Zhang et al., 2019). Our study indicates that not all ORNs are equal in their circuit function, and that genetically predetermined morphometric differences between compartmentalized ORNs underlie their functional disparity.

Our recent studies also identified the courtship-promoting Or47b ORNs as a neural substrate for a fly reproductive hormone, named juvenile hormone. We showed that the sensitivity of Or47b ORNs to an aphrodisiac pheromone is low in immature young males but high in older males at peak fertility ( Lin et al., 2016). This age-dependent sensitization permits coordination of courtship activity with reproductive maturity, thereby providing a means to increase male reproductive fitness. Building on these findings, we further identified a signal amplification mechanism by which olfactory responses can be amplified in insect ORNs in response to juvenile hormone signaling ( Ng et al., 2019). Surprisingly, this amplification mechanism only applies to courtship-promoting ORNs—O47b and Ir84a neurons—among the ˜50 ORN types in the antenna. Together, our finding reveals the surprising complexity of insect olfactory transduction: not all ORNs expressing receptors of the same class employ identical transduction mechanisms. Rather, a common transduction channel can function downstream of two distinct classes of receptors.