No premature gene expression in germ cells of embryos deriving from nos females

The product of nos is required at the posterior pole of the embryo for the differentiation of abdominal structures, but not for pole cell formation. A previous analysis that reported the expression of germline-specific enhancer-trap lines suggested that nos also controls the timing of the initiation of transcription of germline-specific genes. Here we repeat the experiments that led to this hypothesis and we report further experiments. Our results show that, contrary to what had been reported, germ cells of embryos deriving from nos females do not show premature gene expression. Germ cells of such embryos, however, often show artefactual lacZ staining even in the absence of a lacZ gene.