Phenotype of the yao plant. A-B: Photographs showing full seed set in wild-type (A) and partial seed set in yao/+ mutant siliques (B). C-L: Micrographs of cleared ovules from the same yao/+ silique showing the wild-type (+/+) embryo at the globular stage (C), and yao/yao mutant ovules (D-L). Mutant zygotes were either arrested (D-E) or divided once with misplaced division plane (F-G) and an enlarged apical cell (H-J). The abnormal apical cells divided transversely (K-L). ac, apical cell; bc, basal cell; ep, embryo proper; su, suspensor; z, zygote. Arrowheads indicating enlarged nucleoli. Bar = 20 μm.