Olfactory responses in a gustatory organ of the malaria vector mosquito Anopheles gambiae

The proboscis is an important head appendage in insects that has primarily been thought to process gustatory information during food intake. Indeed, in Drosophila and other insects in which they have been identified, most gustatory receptors are expressed in proboscis neurons. Our previous character...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2006-09, Vol.103 (36), p.13526-13531
Main Authors: Kwon, H.W, Lu, T, Rützler, M, Zwiebel, L.J
Format: Article
Language:English
Subjects:
Anatomy & physiology
Animals
Anopheles - anatomy & histology
Anopheles - cytology
Anopheles - genetics
Anopheles gambiae
Appendages
Biological Sciences
Brain
Butylamines
Drosophila
Electrodes
Electrophysiology
Female
gene expression
Genes, Insect
human-related odorants
Immunohistochemistry
Insect vectors
Insect Vectors - genetics
Insect Vectors - physiology
labial olfactory sensillum
Malaria
Malaria - transmission
messenger RNA
Mosquitoes
Mosquitos
Neurons
odors
Olfactory Pathways - physiology
Olfactory Receptor Neurons - physiology
Olfactory Receptor Neurons - ultrastructure
olfactory receptors
Proboscis
Receptors, Odorant - genetics
Receptors, Odorant - metabolism
Receptors, Odorant - physiology
Sensilla
Smell
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Summary:The proboscis is an important head appendage in insects that has primarily been thought to process gustatory information during food intake. Indeed, in Drosophila and other insects in which they have been identified, most gustatory receptors are expressed in proboscis neurons. Our previous characterization of the expression of AgOR7, a highly conserved odorant receptor (OR) of the Afrotropical malaria vector mosquito Anopheles gambiae in the labellum at the tip of the proboscis was suggestive of a potential olfactory function in this mosquito appendage. To test this hypothesis, we used electrophysiological recording and neuronal tracing, and carried out a molecular characterization of candidate OR expression in the labellum of A. gambiae. These studies have uncovered a set of labial olfactory responses to a small spectrum of human-related odorants, such as isovaleric acid, butylamine, and several ketones and oxocarboxylic acids. Molecular analyses indicated that at least 24 conventional OR genes are expressed throughout the proboscis. Furthermore, to more fully examine AgOR expression within this tissue, we characterized the AgOR profile within a single labial olfactory sensillum. This study provides compelling data to support the hypothesis that a cryptic set of olfactory neurons that respond to a small set of odorants are present in the mouth parts of hematophagous mosquitoes. This result is consistent with an important role for the labellum in the close-range discrimination of bloodmeal hosts that directly impacts the ability of A. gambiae to transmit malaria and other diseases.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0601107103