Genomic analysis of the diapause program in the West Nile virus vector Culex pipiens.

Abstract

The Culex pipiens complex of mosquitoes is a major vector for several pathogens responsible for infectious human diseases including West Nile virus in North America. With the growth of the American population, the prevalence of vector-borne diseases has become an increasing threat to human safety. This complex of mosquitoes includes the northern house mosquito Culex pipiens form pipiens, the underground mosquito Culex pipiens form molestus, and the southern house mosquito Culex quinquefasciatus. While each of these closely related mosquitoes share similar morphology, they all employ unique life strategies suited to their unique ecological niches, including overwintering diapause, host biting preference, ecological niche distribution and reproductive strategies. Despite these similarities and differences historically being obstacles to the control of these mosquitoes, new molecular technologies have enabled us to use these factors as a foundation for novel forms of vector control. Diapause is an overwintering dormancy characterized by a suite of adaptations in response to seasonal changes. As survival mechanisms in anticipation of harsh winter conditions, these adaptations include alterations in the female Culex pipiens form pipiens life cycle such as increased stress tolerance, increased nutrient allocation and alternative reproductive development. In Culex pipiens form pipiens, it is initiated by the shortened day lengths of fall. One of the main obstacles in vector control of the Culex pipiens complex of mosquitoes is accurate identification of specimens, which relied on the historically unreliable measurement of the dorsal and ventral arms of the male phallosome (genetalia). Here we offer high resolution melting curve analysis which allows the use of fixed, single nucleotide polymorphisms (SNPs) to cheaply and quickly validate the identities of mosquito specimens. Isolating and disruption of genes contributing to the life strategies of Culex pipiens complex mosquitoes is central to control of these vectors. Fortunately, the shared ancestry and divergent genetics of these mosquitoes provides an excellent opportunity for mapping studies, and consequently identification of candidate genes for disruption. The next chapters describe development of SNP markers for genetic mapping, and transcriptomic analysis utilizing RNAseq technologies to simultaneously identify and quantify expression differences between Culex pipiens biotypes and diapausing and nondiapausing specimens.