Sex determination is an extraordinarily complex mechanism. During this process, signals of different nature (genetic, epigenetic, environmental, etc.) interact with each other, often in a hierarchical manner, to produce a male or a female embryo. Historically, the study of sex determination has relied on insect models (specially the fruit fly Drosophila) due to their short generation time as well as to the presence of very well developed genetic toolkits.
Ten years ago we started a collaboration focused on this topic with the laboratory of Dr. Lucas Sanchez at the CIB-CSIC (Spanish Research Council, Madrid), investigating the evolution of the different components (proteins and genes) of the sex determination cascade in insects. Our latest results on this subject have been published this week by the journal Genetics. In this work we describe an unusual variation in the sex determination mechanism of sciara flies (gnats). More specifically, we find that the gene doublesex (responsible for discriminating between male-specific and female-specific developmental plans) does not seem to play that role in these insects, as suggested by the presence of non sex-specific doublesex transcripts in both males and females. This feature sets Sciara apart from other insects, revealing not only their divergent nature but also the extreme plasticity of sex determination mechanisms in nature.
