Targeted identification of markers linked to malaria and filarioid nematode parasite resistance genes in the mosquito Aedes aegypti

Quantitative trait loci (QTL) have been identified for competence of the mosquito Aedes aegypti to transmit the avian malaria parasite Plasmodium gallinaceum and the human filarial parasite Brugia malayi. Efforts towards the map-based cloning of the associated genes are limited by the availability of genetic markers for fine-scale mapping of the QTL positions. Two F2 mosquito populations were subjected to bulked segregant analysis to identify random amplified polymorphic DNA (RAPD)-PCR fragments linked with the major QTL determining susceptibility to both parasites. Individual mosquitoes for the bulks were selected on the basis of their genotypes at restriction fragment length polymorphism (RFLP) loci tightly linked with the QTL. Pool-positive RAPD fragments were cloned and evaluated as RFLP markers. Of the 62 RAPD/RFLP fragments examined, 10 represented low-copy number sequences. Five of these clones were linked with the major QTL for P. gallinaceum susceptibility (pgs1), of which one clone mapped within the flanking markers that define the QTL interval. The remaining five clones were linked with the major QTL for B. malayi susceptibility (fsb1), and again one clone mapped within the flanking markers that define the QTL interval. In addition, nine RAPD/RFLP fragments were isolated that seem to be of non-mosquito origin.