Model of the Regulation of Ovule Development

[Click on the pathway to view scanning electron micrographs of the ovules represented here.]

The overall pathway of Arabidopsis ovule development is represented in this figure as a series of key developmental stages connected by the processes which are required to achieve each stage. The developmental progression occurs from left to right and is subdivided into the three main parallel pathways of nucellar, chalazal, and funicular development. The chalazal development pathway is further subdivided into separate pathways for each of the two integuments. Within each integument there is separate control of cell division and cell expansion. White arrows indicate the normal progression through the ovule development pathway. The processes which the arrows represent are described in Roman letters next to the arrows. Labels in upper case italics indicate the points of action of wild-type genes in the pathway. Thin yellow arrows, labeled in lower case italics, indicate deviations from the pathway caused by specific mutations. The phenotypes of the mutants at anthesis are illustrated in pale green to show the results of the deviations from the wild-type pathway. The thick red arrow represents the promotion of embryo sac development by the inner integument. Question marks indicate genes predicted to exist by the model which have not yet been identified.

es, embryo sac; mmc, megaspore mother cell.