Fig. 2. The CycB NRE confers regulation on hb mRNA exclusively in the PGCs. Accumulation of Hb in embryos from wild-type (wt) females or females carrying the indicated hb transgene, with high magnification views (of other embryos) shown below to allow visualization of the pole cells (marked with arrowheads). Accumulation in the anterior 50% of the embryo derives from both unrepressed maternal mRNA and zygotically transcribed mRNA; accumulation in the posterior 50% of the embryo derives primarily from unrepressed maternal mRNA (in the transgenic embryos), with a minor contribution at the stage shown from zygotic transcription under the control of the terminal system (most easily seen in the wild-type embryo).