Embryos, isolated from adult worms grown on OP50 with no added heme, expressed the
hrg-1::gfp reporter in all somatic cells post-gastrulation. However, as the embryo entered the 100-cell stage, GFP was significantly enhanced in intestinal precursor cells, compared to the surrounding cell types. As the embryos matured, GFP expression was continually maintained in the presumptive intestinal cells but was undetectable in non-intestinal cells. These results indicate that although
hrg-1 is initially expressed in all somatic cells of the C. elegans embryo,
hrg-1 expression is greatly enhanced in early intestinal cells with either a concomitant loss of activation or active repression in non-intestinal cells.