Figure 4.

Promoter-GUS expression during early seed development. GUS reporter constructs were made for a selection of transcription factors to assess their use as markers for early endosperm development. A to E, Expression of the At1g65300 (AGL38/PHE2) construct was seen in mature pollen (B) and subsequently in the central cell after fertilization (A). Expression then persisted in the very early embryo and endosperm (C) but became restricted to the endosperm around the late globular stage (D). Expression was then specific to the chalazal region during transition (E). F, The At1g49190 (ARR19) promoter was expressed in the chalazal endosperm during globular and early heart stages of seed development. G, The At5g60440 (AGL62) promoter was expressed throughout the syncytial endosperm, albeit at low levels, and is shown here during the globular stage. H, The At4g18870 (HSF15) promoter had very strong expression in the chalazal endosperm plus strong expression in the peripheral endosperm at the globular stage of development. Staining was not apparent in the micropylar domain. I and J, The At4g21080 (DOF4.5) promoter showed very strong chalaza-specific expression at the globular stage (I), with expression becoming more widespread in the endosperm at the heart stage (J). The labels on E are as follows: cze, chalazal endosperm; em, embryo; mpe, micropylar endosperm; pe, peripheral endosperm.