Professor of Genetics, Genomics and Development*
*Affiliate, Division of Neurobiology, and Member of the Helen Wills Neuroscience Institute
We study taste recognition in the fruit fly, Drosophila Melanogaster, to examine how sensory information is processed by the brain. We use a combination of molecular, genetic, electrophysiological and behavioral approaches to study taste circuits. Our aims are to understand how different tastes are distinguished by the brain and how taste percepts and behaviors are modified by experience.
The gustatory system in Drosophila is crucial for detecting food, selecting sites to lay eggs and recognizing mates. Taste neurons are distributed on many parts of the fly's body surface and they recognize taste stimuli such as sugars, salts, acids, alcohols and noxious chemicals. We have recently characterized a large family of ~60 candidate gustatory receptor genes (GRs). These receptors provide essential molecular markers that we are using to examine taste recognition both in the periphery and in the CNS.
Ligand specificity and behavioral specificity of different gustatory receptors. To understand the function of different gustatory neurons, we are determining the ligands that different taste neurons recognize and the behaviors that they mediate. We are identifying ligands by a combination of genetic cell ablations and receptor misexpression studies, coupled with behavioral paradigms and calcium imaging experiments to assay taste responses. For example, gustatory neurons containing the same receptor gene can be ablated by genetically expressing a toxin and taste defects can be tested by simple behavioral assays, like food choice discrimination measured by food-coloring uptake. We are also expressing calcium-sensitive flourescent proteins in taste neurons-this allows us to monitor taste responses in the entire population of gustatory neurons in vivo with single cell resolution. We recently identified different taste cell populations that recognize bitter compounds, sugars, carbon dioxide or water using these approaches. It will be interesting to determine whether there are specialized cells for salts, acids and fat as well. These studies provide a basis for understanding taste detection in the periphery.
Information processing in the brain. The subesophageal ganglion of the fly brain contains both axons of gustatory neurons and dendrites of motor neurons involved in taste behaviors. This suggests that the fly may have simple and localized taste circuits, with few connections between sensory stimulus and motor response. In addition, projection neurons may relay gustatory information to higher brain centers, perhaps for more complex associations. We are interested in mapping the functional and anatomical components of taste circuits using a variety of approaches. Genetic approaches to label subsets of neurons in the brain, behavioral screens for taste mutants, and calcium imaging of taste responses in the brain will help elucidate these circuits. These studies will provide insight into the integration of gustatory cues and the difference between sweet versus bitter, and will set the stage to examine how taste circuits are modified by learning and other sensory stimuli. We plan to study increasingly complex problems of neural integration by examining how different stimuli impinge upon taste circuits.
Modulation of taste behaviors by hunger and satiety. For an animal to survive in a constantly changing environment, its behavior must be shaped by the complex milieu of sensory stimuli it detects, its previous experience and its internal state. Although taste behaviors in the fly are relatively simple, with sugars mediating acceptance behavior and bitter compounds avoidance, these behaviors are also plastic and modified by intrinsic and extrinsic cues. One long term goal is to examine how internal states influence taste circuits and behaviors by identifying neuropeptides, receptors and cells which modulate taste behavior.
Contact chemoreceptors mediate male-male repulsion and male-female attraction during Drosophila courtship. [R. Thistle, P. Cameron, A. Ghorayshi, L. Dennison and K. Scott (2012) Cell 149, 1140-1151]
Dopaminergic modulation of sucrose acceptance behavior in Drosophila [S. Marella, K. Mann and K. Scott (2012) Neuron 73, 941-950]
The molecular basis for water taste in Drosophila. [P. Cameron, M. Hiroi, J. Ngai, and K. Scott (2010) Nature 465, 91-95]
Motor control in a Drosophila taste circuit. [M.D. Gordon and K. Scott (2009) Neuron 61, 373-384]
The detection of carbonation by the Drosophila gustatory system. [W. Fischler, P. Kong, S. Marella, and K. Scott (2007) Nature 448, 1054-1057]
Imaging taste response in the fly brain reveals a functional map of taste category and behavior. [S. Marella, W. Fischler, P. Kong, S. Asgarian, E. Reukhert, and K. Scott (2006) Neuron 49, 285-295]
Taste recognition: Food for thought. [K. Scott (2005) Neuron 48, 455-464, Review]
Taste Representations in the Drosophila Brain.[Z. Wang, A. Singhvi, P. Kong and K. Scott (2004) Cell 117, 981-991]
Photo Credit: Mark Hanson of Mark Joseph Studios
Last Updated 2012-08-08