SUMMARY/ABSTRACT: Here we seek to understand the evolution of resistance to pyrethroid insecticides in Aedes aegypti, an important vector of human diseases such as dengue and Zika. Pyrethroid insecticides are widely used for control of adult Aedes, but resistance has evolved in many populations, representing a global challenge for control of this vector and the diseases it transmits. Finding strategies for delaying the development of resistance by mosquito vectors to the few available insecticides is critical. To do so, it is essential to identify the mutations responsible for resistance in order to design sensitive and precise monitoring programs, to understand the population genetics and the evolution of resistance, and to design effective countermeasures to slow the development of resistance. Our long-term goal is to develop the necessary technologies for monitoring resistance alleles so that this important evolutionary process can be studied and so that the development of resistance can be delayed. Our short-term goal is to determine the mutation responsible for the newly identified pyrethroid resistance locus on chromosome 1 in A. aegypti. To address our short-term goal, we will pursue two specific aims: Aim 1. Determining the resistance locus on chromosome 1 with high resolution. Aim 2. Evaluation of candidate genes at the resistance locus on chromosome 1 and validation of the mutation causing resistance. A substantial amount of preliminary data has been obtained in support of this proposal. In addition to the susceptible ROCK and well characterized SP strains, we have isolated two congenic resistant strains. The CKR strain contains the resistance factors from the SP strain introgressed into the background of the ROCK strain, and the KR strain contains only the kdr mutation in the background of ROCK. We have also conducted a transcriptomic (RNAseq) and proteomic analysis of these strains which will facilitate our selection of candidate genes at the resistance locus. These experiments will allow us to identify a new pyrethroid resistance mutation in A. aegypti and will give us preliminary information about its frequency in other populations of A. aegypti from across the globe. These data will provide new information about the similarities and differences that insecticide selection has had on geographically distant populations. Our results will form the basis for future studies of resistance monitoring and resistance management in this important vector of human disease.