Insects use their antennae for smelling and thus for locating resources in their environment. Max Planck researchers now present the first complete analysis of genes involved in antennal olfaction of the tobacco hornworm Manduca sexta. Approximately 70 different receptors expressed in some 100 000 neurons allow these moths to detect a large number of odors and to perform odor-guided behaviors. This is the first essentially complete antennal transcriptome characterized in a non-model insect. Insects have a highly sensitive sense of smell. Extremely low concentrations of odor molecules in the air are sufficient to be detected by receptor neurons on their antennae. Specific proteins, so-called receptor proteins, expressed in these neurons recognize the odors. The odor molecules bind to the receptors and produce chemical and electrical signals that are processed in the insect brain and eventually affect the insect's behavior. Apart from the receptors, further proteins involved in olfaction, including enzymes and chemosensory proteins, come into play. Based on these molecular principles, all insects follow their innate and elementary survival formula: finding food, recognizing mates, and − in the case of females − identifying adequate oviposition sites that guarantee nutritious and easily digestible food for their offspring. Moths are popular research objects in addition to fruit flies. The genome of the silkworm Bombyx mori has been fully sequenced; however, this insect has been domesticated by humans for thousands of years, therefore its native conspecifics cannot be found anymore.
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