Fig. 2. Embryo development is delayed in 826 hemizygotes and arrests prematurely in 826 homozygotes. Whole-mount analysis of developing seeds from plants hemizygous for the 826 T-DNA. (A-C) Representative seeds from three siliques in subsequent stages of development. Indices (i-iii) indicate the different classes of embryos found in the same silique. When development of wild-type embryos is at the torpedo (Ai), bent-cotyledon (Bi) or mature stage (Ci), 826 hemizygous embryos have only reached the heart (Aii), torpedo (Bii) or bent-cotyledon stage (Cii). At all later time points, homozygous 826 embryos remain arrested at the globular stage (Aiii, Biii, Ciii). The arrested embryos display storage structures typical for late wild-type embryo development (D). Histochemical staining of seeds from the same silique reveals that the GUS activity correlates with the delay in embryo development. GUS expression is absent in mature embryos (Ei), whereas weak and strong expression is observed in respectively delayed torpedo stage (Eii) and arrested globular stage embryos (Eiii).