Figure 6.

AtFIS2:GUS Expression during Early Ovule Development in Hieracium.

Ovules from sexual Hieracium P4 ([A] to [D]), apomictic Hieracium D3 ([E] to [H]), and apomictic Hieracium A3.4 ([I] to [L]) were stained with GUS and viewed whole-mount using dark-field microscopy ([A], [E], and [I]) or Nomarski DIC microscopy. The numbers at top right indicate the ovary stage (Koltunow et al., 1998). Bars = 50 μm in (A), (E), (I), and (L) and 25 μm in (B) to (D), (F) to (H), (J), and (K).

(A) P4 ovule in the chalazal (ch)-to-micropylar (mp) orientation showing GUS stain as pink.

(B) Enlarging selected spore (ss) and blue GUS-stained degenerating megaspores (dms) surrounded by the nucellar epidermis (ne). Indicated structures are outlined with solid lines.

(C) Enlarging functional megaspore (fm) with a large nucleus (n) chalazal to degenerated megaspores. Indicated structures are outlined with solid lines.

(D) Ovule containing an early embryo sac (es) containing dividing embryo sac nuclei (esn) and surrounded by the endothelium (et).

(E) D3 ovule showing the corresponding stage of apomictic development to (A).

(F) Enlarging aposporous initial cell (ai) at the corresponding stage of apomictic development to (B). The aposporous initial cell, outlined with a broken line, forms in a slightly different plane than the other structures, which are outlined with solid lines.

(G) Enlarging aposporous initial cell above two smaller initial cells.

(H) D3 ovule containing a dividing aposporous embryo sac (aes) with embryo sac nuclei at the corresponding stage of apomictic development to (D).

(I) A3.4 ovule showing the corresponding stage of apomictic development to (A) and (E).

(J) Enlarging aposporous initial cells at the corresponding stage of apomictic development to (B) and (F). Multiple aposporous initial cells are indicated with broken lines, and some form in slightly different planes compared with the sexual structures, which are outlined with solid lines.

(K) Enlarging aposporous initial cells.

(L) Aposporous embryo sac structures at the corresponding stage of apomictic development to (D) and (H).