Mechanisms of chemosensory behavioral plasticity in C. elegans

Brandeis University, Waltham MA

Investigators

Abstract

All animals sense and respond to multiple chemicals in their environment. Chemical cues signal the presence of food, mates, predators, and toxic substances, and animals are attracted, repelled, or indifferent to individual odors. However, the responses of animals to chemicals are not fixed, but can be altered by their past experience and current state. For example, prolonged prior exposure to an odor decreases subsequent responses to that chemical, and juveniles and adults can exhibit different responses to chemicals. This flexibility ensures that the animal exhibits the behavior that is most appropriate for its current condition. The overall goal of this project is to explore how an animal's experience and its developmental stage alter the functions of the nervous system to drive different chemical-sensing behaviors. Given the importance of smell and taste in animal lifecycles, this work allows us to begin to explore how changes in the environment may impact animal welfare, and aid in animal husbandry and conservation efforts. The proposed work supports the training of high school, undergraduate and graduate students, and postdoctoral fellows, and all efforts will be made to involve members of underrepresented minority groups. The project also builds research relationships between university labs and high school students and teachers. The insights from this work are shared with the public via hands-on demonstrations at local science museums and science fairs. The proposed work also incorporates collaborations among biologists, chemists and bioengineers, and is thus expected to promote interdisciplinary learning and innovation. Both innate and learned behaviors are flexible, and are extensively modulated by an animal's experience as well as its external and internal state. The specific goal of this proposal is to identify and characterize the molecules, neurons, and circuits that mediate context- and developmental stage-specific plasticity in chemosensory behavioral responses of the nematode C. elegans. Preliminary experiments suggest that contextual cues modulate the output of antagonistic neural circuits to toggle the response to a simple alcohol between attraction and aversion. The behavioral strategies and neuronal mechanisms underlying this response flexibility is characterized using high-resolution analyses of behavioral states and neuronal activity under defined conditions. C. elegans chemosensory behaviors are also dramatically modulated as a function of developmental stage and environmental experience. The proposed research characterizes this experience- and stage-dependent chemosensory behavioral plasticity, and identifies the required neuronal and molecular mechanisms. Results from this work provide new information about the mechanisms by which animals efficiently alter their behaviors in response to changing external and internal conditions.