Nixalone is sufficient to convert femaleAedes aegyptiinto fertile males andmyo-sexis needed for male flight

Abstract

A dominant male-determining locus (M-locus) establishes the male sex (M/m) in the yellow fever mosquito,Aedes aegypti.Nix, a gene in the M-locus, was shown to be a male-determining factor (M factor) as somatic knockout ofNixled to feminized males (M/m) while transient expression ofNixresulted in partially masculinized females (m/m), with male reproductive organs but retained female antennae. It was not clear whether any of the other 29 genes in the 1.3-Mb M-locus are also needed for complete sex-conversion. Here, we report the generation of multiple transgenic lines that expressNixunder the control of its own promoter. Genetic and molecular analyses of these lines provided insights unattainable from previous transient experiments. We show that theNixtransgene alone, in the absence of the M-locus, was sufficient to convert females into males with all male-specific sexually dimorphic features and male-like gene expression. The converted m/m males are flightless, unable to perform the nuptial flight required for mating. However, they were able to father sex-converted progeny when presented with cold-anesthetized wild-type females. We show thatmyo-sex, a myosin heavy-chain gene also in the M-locus, was required for male flight as knockout ofmyo-sexrendered wild-type males flightless. We also show thatNix-mediated female-to-male conversion was 100% penetrant and stable over many generations. Therefore,Nixhas great potential for developing mosquito control strategies to reduce vector populations by female-to-male sex conversion, or to aid in a sterile insect technique that requires releasing only non-biting males.