[
International Worm Meeting,
2021]
The ability to discriminate between nutritious and harmful food is essential to survival. As a result, learned avoidance to harmful food sources is conserved from invertebrates to humans. The mechanisms enabling the nervous system to associate sensory cues from a food source with an internal state of sickness to trigger aversive memory formation remain elusive. After prolonged exposure to pathogenic food, C. elegans can learn to avoid the pathogen upon subsequent encounter1. This learned aversion requires infection; non virulent forms of bacteria are not sufficient for memory formation. In response to exposure to pathogenic food, serotonin is induced in a pair of sensory neurons called ADF and remodels downstream circuits2. Learned aversion to pathogen requires serotonin signaling from ADF, suggesting that ADF serves as a site of integration for detecting bacterial cues and internal sickness caused by the pathogen. We seek to understand how internal state changes the coupling between sensory activation and serotonin release in ADF neurons. As a first step, we are using calcium imaging to examine ADF responses to bacterial cues in both naive and pathogen-exposed animals. ADF responds robustly to conditioned media from both pathogenic and non-pathogenic bacteria in a dose-dependent fashion, and ADF activity can be modulated by previous odor history. We are screening mutants using these quantitative parameters to assess ADF responses to direct chemosensory stimuli, indirect signaling from other sensory neurons, and signaling from non-neuronal tissues indicating bacterial infection. Our goal is to uncover cell-biological mechanisms through which ADF neurons mediate learned pathogenic behavior in C. elegans. 1. Zhang, Y., Lu, H., & Bargmann, C.I. (2005). Pathogenic bacteria induce aversive olfactory learning in Caenorhabditis elegans. Nature, 438(7065), 179. 2. Morud, J., Hardege, I., Liu, H., Wu, T., Basu, S., Zhang, Y., & Schafer, W. (2020). Deoprhanisation of novel biogenic amine-gated ion channels identifies a new serotonin receptor for learning. bioRxiv. doi: https://doi.org/10.1101/2020.09.17.301382.