Nix alone is sufficient to convert female Aedes aegypti into fertile males and myo-sex is needed for male flight

A. Aryan, M. A. E. Anderson, J. K. Biedler, Y. M. Qi, J. M. Overcash, A. N. Naumenko, M. V. Sharakhova, C. H. Mao, Z. N. Adelman and Z. J. Tu,  Proceedings of the National Academy of Sciences of the United States of America,  117:17702-17709. 2020.

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 of Nix led to feminized males (M/m) while transient expression of Nix resulted in partially masculin-ized 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 express Nix under the control of its own promoter. Ge-netic and molecular analyses of these lines provided insights un-attainable from previous transient experiments. We show that the Nix transgene 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 mat-ing. However, they were able to father sex-converted progeny when presented with cold-anesthetized wild-type females. We show that myo-sex, a myosin heavy-chain gene also in the M-locus, was re-quired for male flight as knockout of myo-sex rendered wild-type males flightless. We also show that Nix-mediated female-to-male conversion was 100% penetrant and stable over many genera-tions. Therefore, Nix has 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.


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