ODORANT-BINDING PROTEINS AND HOST SEEKING PREFERENCEIN THE MALARIA VECTOR ANOPHELES GAMBIAE

T. Proebstl¹, R.A. Steinbrecht¹, G. Ziegelberger¹,J. Ziesmann¹, K.E. Kaissling¹,
L.J. Zwiebel² and F.C. Kafatos^2
1Max-Planck-Institut fuer Verhaltensphysiologie, D-82319Seewiesen, Germany
²European Molecular Biology Laboratory , D-69117 Heidelberg,Germany

The role of olfaction in host seeking and selection is well establishedfor anopheline mosquitoes, the principle vectors for malaria. Any interferencewith olfactory signal transduction in these hematophagous insects may presentan attractive means to control the trans-mission of malaria. The basicmechanisms of insect olfactory signal transduction, however, have mainlybeen studied in moths. A particularly accessible component of the olfactory-specificsignal transduction cascade are the odorant-binding proteins (OBPs) presentin the sensillum lymph of insect olfactory sensilla. These low molecularweight proteins are thought to selectively transport odorants to membrane-boundreceptor molecules in order to initiate signal transduction and thereafterto deactivate the stimulus. In moths, different OBPs are found in sensillaresponsible for pheromone detection and in sensilla tuned to plant odours.A combined effort involving biochemical, electrophysiological, molecular,and topochemical approaches has begun to characterize OBPs in Anophelesgambiae. The generation of subtracted cDNA libraries specifically enrichedfor genes expressed in the olfactory structures of female adult mosquitoesis described. Preliminary data suggest that an initial screening has resultedin the isolation of the first OBP encoding cDNAs from A. gambiae.Furthermore, studies to localize OBPs in the different antennal sensillumtypes and to correlate this localization with the olfactory specificityof these sensilla as revealed by electrophysiology have started. The maingoal of this project is to identify OBPs associated with sensilla involvedin host-odour detection.