My picks for today:
Segregation of Odor Identity and Intensity during Odor Discrimination in Drosophila Mushroom Body:
Considerable progress has been made in understanding how olfaction works as the receptor proteins, sensory neurons, and brain circuitry responsible have become increasingly well-characterized. However, olfactory processing in higher brain centers, where neuronal activity is assembled into the perception of odor quality, is poorly understood. Here, we have addressed how the mushroom body (MB)--a secondary olfactory center--is involved in olfactory discrimination. We manipulated the MB by ablation, disruption of synaptic transmission, and interruption of key cellular signaling molecules in naïve flies and in flies trained to discriminate odors. We first show that although both odor identity and intensity are encoded in the MB, only the former requires Gαq-dependent signaling and is necessary for naïve flies to spontaneously discriminate different odors. We then show that training flies to alter their olfactory response requires Gαs-mediated signaling in MB for both odor intensity and odor identity. We have thus identified (i) segregation of odor identity and odor intensity at the MB level in naïve flies and (ii) different G-protein-dependent signaling pathways for spontaneous versus experience-dependent olfactory discrimination.
Viral Evolution in the Genomic Age:
Genome sequence data will undoubtedly deliver much to the study of viral pathogens and their diseases. A prominent example of this new genomic perspective is influenza A virus, for which a large-scale genome sequencing project begun in the year 2005 has, to date, generated around 2,500 complete viral genomes [1]. While this alone is newsworthy, the rise of rapid, high-throughput genome "pyrosequencing" promises to take the production of viral genomes to a level once unimaginable [2].
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