An Epigenetic Perspective on Developmental Regulation of Seed Genes Zhang Heng , Ogas Joe   Molecular Plant  Volume 2, Issue 4, Pages 610-627 (July 2009) DOI: 10.1093/mp/ssp027 Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 1 Embryogenic Pathways in Flowering Plants. A typical plant life cycle (black arrow) is depicted with major biological events. The sporophytic and gametophytic stages of the life cycle are separated by a thin dashed line. Nonzygotic embryogenesis is separated into somatic embryogenesis (green dashed arrow) and apomixis (red arrow), which is a naturally occurring nonzygotic pathway leading to seed production that arises from ovule cells (sporophytic apomixis) or from cells of an unreduced embryo sac (gametophytic apomixis). Arabidopsis genes discussed in this review that contribute to zygotic and/or somatic embryogenesis are indicated. Molecular Plant 2009 2, 610-627DOI: (10.1093/mp/ssp027) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions

Figure 2 Diagram of Key Events and Players in Chromatin-Based Repression of Seed-Specific Genes. A generic seed gene with nucleosomes and transcription start site (TSS) is depicted. Binding of VAL proteins to the promoter region of the gene is proposed to initiate the repressive state by recruiting PKL and PcG proteins to the promoter region (blue dashed arrow), leading to remodeling of nearby nucleosomes and specifically methylation of histone H3 lysine 27 (H3K27me3). It remains to be determined how the extent of deposition of H3K27me3 is delimited. Binding of LHP1 and other factors to H3K27me3-enriched regions of chromatin is thought to contribute to the repressed state. PKL and PcG proteins are also required for maintenance of this chromatin structure. The chromatin template is reset by an unknown mechanism when the cells re-enter the embryogenesis developmental program. For details, see text. Molecular Plant 2009 2, 610-627DOI: (10.1093/mp/ssp027) Copyright © 2009 The Authors. All rights reserved. Terms and Conditions