Sex Determination in Mosquitoes

Abstract

Abstract Sexual reproduction is critical to the survival and evolution of many organisms including mosquitoes. Sex determination in insects is often initiated by a fast-evolving primary signal(s) that switches on or off a cascade of molecular events that lead to sex-specific splicing of the transcripts of doublesex ( dsx ) and fruitless ( fru ), two genes that encode highly conserved transcription factors. The sex-specific isoforms of the DSX and FRU proteins programme sexual dimorphism in Drosophila melanogaster and other insects, and sex-specific splicing of dsx and fru is the molecular output of the process of sex determination. Sex-biassed splice isoforms of dsx and fru have been identified in mosquitoes although what regulates their splicing is unknown. Previous genetic evidence suggests, depending on the mosquito species, that a dominant male-determining factor (M-factor) from either the Y chromosome or a male-determining locus (M-locus) is the primary signal that initiates male development and controls sex determination. In this chapter, we focus on recent progress in deciphering the molecular mechanisms of sex determination in mosquitoes, including the discovery of complex and distinct dsx splicing patterns in three mosquito genera, and the discovery and characterization of the first M-factor in Aedes aegypti and additional M-factor candidates in divergent mosquito species. We discuss recent discoveries of the genetic content and rapid remodelling of the Y chromosomes in the Anopheles gambiae species complex and the molecular consequence of Y chromosomal decay. We end by discussing the remaining challenges in illustrating the entire sex determination pathway in mosquitoes, and in developing novel mosquito control strategies based on reducing the number of blood-sucking females or converting them into harmless males.