Female gametophyte development revealed by laser scanning confocal microscopy in wild-type and CTF7 overexpression plants. A to H, Wild-type female gametophyte development. I to L, Female gametophyte development in CTF7 overexpression lines. A, Female gametophyte stage 1 (FG1) ovule showing the functional megaspore (M). A trace of the degraded megaspore (DM) is still visible. Ch, Chalaza. B, FG2 ovule with a two-nucleate (N) embryo sac. The degraded megaspore is still visible in some cases. C, FG3 ovule showing a late two-nucleate embryo sac with an enlarged central vacuole (V) and a small chalazal vacuole. D, Ovule with a four-nucleate embryo sac at FG4. E, Ovule with an embryo sac at FG5. Cellularization and cell differentiation are complete with the formation of two synergid nuclei (SN), an egg nucleus (EN), three antipodal nuclei (AN), and the two prominent polar nuclei (PN), which have not yet fused. F, Ovule with a mature seven-celled embryo sac at FG6. The polar nuclei have fused to form a diploid central nucleus (CN). G, Ovule at FG7 in which the antipodal cells have begun to degenerate. H, Ovule after fertilization. One synergid cell is degraded and the endosperm has completed several rounds of nuclear division. I, 35S-CTF7 ovule. No difference with wild-type FG1 ovules is apparent. The degraded megaspore is visible. J, 35S-CTF7 ovule. The embryo sac is enlarged but the female gametophyte remains at FG1. K, 35S-CTF7 ovule. The female gametophyte completed one round of mitosis. L, 35S-CTF7 ovule. The female gametophyte is degraded. Bars = 5 μm.