The Medfly Sex Determination pathway is partially conserved in the mosquitoes Aedes aegypti: further support to the bottom up evolution model.

In the medfly Ceratitis capitata female sex determination is promoted in XX individuals by an autoregulating master gene, Cctransformer (Cctra ep ), which controls, dsx and fru sex-specific expression and epigenetically maintains its own activity. In XY individuals a Y-linked M factor, still to be identified, represses the activity of Cctra ep . Comparing medfly and Drosophila pathways, only the upstream regulators are apparently different: in Drosophila X-linked elements in XX embryos activate Sxl, which in turn positively autoregulates and activates transformer. In Ceratitis, Cctra ep hence has a novel additional autoregulatory epigenetic function. The Ceratitis Cctra ep .dsx/fru genetic module is widely conserved also in other insect orders, such as Hymenoptera and Coleoptera, but not in the dipteran mosquito Aedes aegypti, neither in the lepidopteran Bombyx mori. An evolutionary perspective of the sex determining genetic pathways in insects will be presented toward a better understanding of this regulatory mechanism in mosquitoes and other diseases vectors, which can be useful for sexing and SIT.