Which protein plays a crucial role in repressing female gene expression in Drosophila?

The DSX protein is a crucial factor in the regulation of sexual differentiation in Drosophila. Specifically, it functions as a transcription factor that influences gene expression based on the sex of the organism. In females, the DSX protein is produced from a different splice form than in males, leading to the repression of various genes that would promote male characteristics. This action is essential for establishing the female phenotype, as DSX binds to specific DNA sequences to inhibit the expression of male-related genes, thereby ensuring that the female developmental pathway is activated and maintained.

In the context of Drosophila sex determination, the function of DSX is closely linked to the ratios of sex chromosomes to autosomes, which determines whether the male or female splice variant is activated. Thus, the role of DSX in repressing female gene expression highlights its importance in the sexual differentiation process and illustrates how molecular mechanisms can dictate developmental outcomes based on genetic signals.