The Polycomb gene FIE is expressed (blue) in unfertilised egg cells of the moss "Physcomitrella patens" (right) and expression ceases after fertilisation in the developing diploid sporophyte (left). In situ GUS staining of two female sex organs (archegonia) of a transgenic plant expressing a translational fusion of FIE-uidA under control of the native FIE promoter.