Fig. 3. Invading PT phenotypes in the feronia mutant. (A-C,H,J) Cleared whole-mount preparations. (D,E,I) Ovules stained with Aniline Blue to visualize the PT. (F,G) Crosses to PT marker line expressing the ß-glucuronidase (GUS) gene. (A) Mature FGs of wild-type and feronia (fer/+) plants before fertilization are indistinguishable from each other and contain synergid cells (sc), egg cell (ec) and central cell (cc). (B) Fertilized wild-type ovules at 24 HAP that contain an elongated zygote (arrow) and free nuclear endosperm (arrowheads). (C) Unfertilized feronia (fer/+) ovule at 24 HAP. The secondary endosperm nucleus (sen) of the central cell and the egg cell nucleus (ecn) are visible. The pollen tube (arrow) enters the ovule but forms an entangled structure (arrowhead) within the FG. (D) Wild-type ovule after fertilization. The PT (arrow) terminated in the micropylar area (mi) of the embryo sac. (E) feronia mutant in which the PT invades the micropylar area (arrow). (F) In wild-type ovules the GUS-activity of the PT remains restricted to the micropylar area of the FG (arrow). (G) In mutant FG the GUS signal is observed in the entire micropylar part of the FG. Owing to the strong GUS activity, the stain diffused into the central cell. (H,I) The PT enters the central cell (arrowheads) after coiling in the micropylar area (arrow). (J) Formation of free nuclear endosperm (arrowheads) after the PT has invaded the FG (arrow). Scale bars: 30 µm.