Testing theories of sex determination and sex chromosome evolution with houseflies

There exists enormous variation between organismal groups in the way sexual fate, i.e. femaleness and maleness, is determined during development and these mechanisms of sex determination are remarkably labile during evolution. This proposal will study the genetic mechanisms and regulation of sex determination, as well as the evolutionary processes responsible for the observed variation by applying the latest genomics technology in housefly (Musca domestica) genetics. The housefly is an exceptional organism in having populations with different sex determination mechanisms, including the standard male heterogametic (XX-XY) system, location of the dominant male determiner (M) on different autosomes, or female heterogamety. The frequency of autosomally located M factors shows clinal variation, being more abundant at higher temperatures. Objectives are to (1) identify the male determining gene(s), (2) test theories about recombination suppression in neo-sex chromosomes, and (3) establish the role of temperature in genetic sex determination. We will sample natural populations for different sex determination mechanisms, set up crosses between existing laboratory strains to map, isolate and characterise M factors, measure local and genome wide recombination frequencies in strains with different sex determination mechanisms and measure temperature effects on sex determination gene expression (transcriptomics). We will exploit the Housefly Genome Project to develop dense marker linkage maps and identify candidate genes for functional analyses. Results are expected to lead to a better understanding of the mechanisms and evolution of sex determination systems and early stages of sex chromosome evolution.

Discovery of gene for maleness in houseflies