FUNCTIONAL-ANALYSIS OF A MOSQUITO GAMMA-AMINOBUTYRIC-ACID RECEPTOR GENE PROMOTER

A single point mutation in the insect gamma-aminobutyric acid receptor (GABAR)-encoding gene (Rdl) confers high levels of resistance to cycl odienes in Drosophila and other insects. We were interested in studyin g the promoter of this gene for two reasons. Firstly, to define the el ements underlying Rdl expression. Secondly, to identify the minimum se t of regulatory elements necessary for construction of a functional Rd l minigene. Such an insecticide-resistance-associated minigene should form a strong selectable marker for use in the genetic transformation of non-drosophilid pest insects, such as mosquitoes. Here, we report t he identification of the region containing the Rdl promoter, via trans ient expression of a luc reporter gene following micro-injection into embryos of the mosquito Aedes aegypti. Promoter activity is contained within a 2.53-kb fragment immediately upstream from the Rdl start codo n. Primer extension shows three closely linked sites for transcript in itiation within this region and sequence analysis reveals a number of putative consensus regulatory sequences shared by other genes expresse d in the nervous system. The implications for construction of a functi onal minigene and the identification of cis-acting control elements un derlying ion-channel gene regulation are discussed.