Fig. 5. Synergid-specific GUS activity of one out of three enhancer detector lines in wild-type and feronia ovules. (A) In mature wild-type ovules before fertilization, the GUS expression is restricted to the synergid cells (sc). (B) The GUS activity decreases significantly in wild-type ovules after fertilization (arrow). (C) In feronia (fer/+) ovules the synergid cells (sc) are stained before fertilization. (D) After PT invasion the GUS activity persists in the synergids (arrow) of mutant feronia embryo sacs. The invading PT appears to be covered by the GUS stain, indicating that it coils within the synergid. Scale bars: 30 µm.