The biology of fish olfaction: amino acids and Ga-proteins

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The sense of smell (olfaction) is a major route by which organisms gather information from their environment. The external cues can induce a diverse array of responses, ranging from internal physiological adjustments to complex behaviours. In fish, dissolved amino acids are essential do numerous behaviours, ranging from food location, to predator avoidance, to migration. At present we know that amino acids can be detected by three morphologically distinct sensory neurons, but what is not known is how these different neurons work together to evoke behavioural responses. The central goal of my research is to help solve this olfactory puzzle, by characterizing what type of olfactory sensory neuron receptor responds to which odorant to eventually evoke a given outcome? My long-term research has three objectives: i) to link olfactory receptors to odours and the organismal responses they evoke, ii) to explore how these relationships may change during the lifecycle of a fish when varying demands are placed on olfaction, and iii) to determine the ramifications of impaired olfaction over such lifecycles. This Discovery proposal details two first steps to meet these objectives. Firstly, in order to link odours to receptors, a pathway is needed to focus research on a subset of the ~150 receptors fish have. I propose to temporarily disable the machinery that links odour receptors to cellular responses as this effectively divides the receptors into four groups. These groups also appear to be associated with different organism-level responses. Secondly, a method is needed to detect what an odour-receptor pairing evokes. As many odours evoke motion, my research will explore how odours evoke different types of activities. The research will also explore how changes in odour perception affect swimming activity, as many natural and synthetic agents impair olfaction. This grant is about the importance of amino acids to olfaction in fishes, and more broadly, it is about how complex signals are perceived and used to direct animals through the changing nature of the present environment.