1a. Objectives (from AD-416):
The objectives of this project are to determine the role of odor receptors (ORs) in chemoreception and behavior of Yellow Fever mosquito, Aedes aegypti and to identify novel compounds that activate or inhibit ORs that may be useful as lures in traps and as repellents.
1b. Approach (from AD-416):
ARS will acquire basic knowledge of odor receptors in the Yellow Fever mosquito, Aedes aegypti. Odor receptors will be expressed heterologously and responses will be recorded from them using the two-electrode voltage clamp technique. The effect of candidate agonists and antagonists will be evaluated for odorant receptor activation or inhibition. Synergistic effects among chemicals may also be evaluated. This information will be used by both parties to jointly discover and develop chemicals for manipulation of mosquito behavior. The Cooperator will provide expertise and advice on olfactory proteins, such as sensory neuron membrane protein (SNMP), and their roles in mosquito behavior. Specifically, the cooperator will utilize immunocytochemical techniques to determine expression patterns of SNMPs to provide insight into potential behavioral roles. Genetic approaches and behavioral bioassays will be developed to further elucidate SNMP role in behavior.
3. Progress Report:
This is a joint effort with the Department of Biological Sciences, University of South Carolina (USC). The function of genes involved in smell in mosquitoes and the related the vinegar fly were tested by inhibiting specific genes and characterizing the physiology and behavior of the resulting insects. Two different transgenic mosquitoes (Ae. aegypti) were made in which the odor receptors OR7 and OR8 were targeted; we confirmed reduced expression of the OR8 gene but not the OR7 gene. The physiology and behavior of mosquitoes in which OR8 expression was reduced by 90% are currently being studied. In other transgenic studies employing vinegar fly (D. melanogaster), the chemosensory SNMP1 and SNMP2 genes were shown to co-express in most olfactory and gustatory sensilla, but in functionally different types of cells. The SNMP2 gene was deleted and behavioral studies comparing the resulting flies with those in which SNMP1 had been deleted showed reduced male-female courtship, but increased male-male courtship in the SNMP2 deleted flies. Flies in which both genes were deleted showed profound behavioral deficits. We hypothesize that the SNMP genes function in the removal/inactivation of chemosensory stimulants. Physiological studies are currently underway to test this hypothesis.