Embryo sac development in WT and <i>ick</i> septuple mutant.

<p>(<b>A—I</b>) DIC observation of embryo sac. Ovules from flowers just before opening were prepared and observed under a microscope with DIC optics. (<b>A</b>) A typical WT embryo sac showing secondary (central, C), egg (E) and synergid (S) nuclei. (<b>B—C</b>) Two optical sections of a septuple mutant ovule showing the embryo sac area with two sets of secondary (C), egg (E) and synergid (S) nuclei. The gamete and synergid nuclei are arranged in a configuration similar to that in the WT and the boundary between the two sets of gametes is clearly visible (arrow in <b>B</b>), indicating the presence of two embryo sacs in the ovule. (<b>D—E</b>) Two optical sections of a mutant ovule with three sets of secondary (C), egg (E) and synergid (S) nuclei. (<b>F—I</b>) Four optical sections of a mutant ovule with four set of secondary (C), egg (E) and synergid (S) nuclei. The synergids for the 3^rd and 4^th sets could not be easily observed. Different sets of gametes in the mutant are indicated by numbers “1”, “2”, “3” and “4”, respectively. The two syngergid nuclei of the same pair are differentiated with or without an “′”, e.g. “S1, S1′, S2, and S2′” referring to two pairs of synergid nuclei. (<b>J—M</b>) Ovules from the septuple mutant carrying a <i>pEC1</i>.<i>1</i>::<i>GUS</i> marker for the egg cell were stained for GUS. The GUS staining shows the presence of one to four egg cells in these ovules. (<b>N—P</b>) Ovules from the septuple mutant carrying a <i>pFIS2</i>::<i>GUS</i> marker for the central cell were stained for GUS. The GUS staining shows the presence of one to three central cells in these ovules. Scale bars in (<b>A</b>), (<b>J</b>), and (<b>N</b>) are for (<b>A—I</b>), (<b>J—M</b>), and (<b>N—P</b>) respectively, and all equal 10 μm.