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Review
, 173 (1), 143-154

Endosperm and Imprinting, Inextricably Linked

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Review

Endosperm and Imprinting, Inextricably Linked

Mary Gehring et al. Plant Physiol.

Abstract

Recent developments advance our understanding of imprinted gene expression in plants.

Figures

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Figure 1.
Figure 1.
Endosperm is an important angiosperm innovation. In gymnosperms, a haploid sperm fertilizes one of the haploid eggs. The embryo develops surrounded and nourished by female gametophyte tissue. In angiosperms, one haploid sperm fertilizes the egg and the other fertilizes the diploid central cell. The central cell is diploid because two haploid nuclei, the polar nuclei, migrate toward one and fuse either before (Arabidopsis) or at the time of (maize) fertilization. The diploid embryo is nourished by the triploid endosperm. A single layer of endosperm remains in mature Arabidopsis seeds; in maize the endosperm supports the germinating seedling.
Figure 2.
Figure 2.
Imprinted genes can be either MEGs or PEGs. Imprinted genes are expressed in a parent-of-origin-dependent manner. Although the diagram depicts complete silencing of one allele, in practice many imprinted genes are differentially expressed between maternal and paternal alleles, not monoallelically expressed.
Figure 3.
Figure 3.
Timing of endosperm cellularization is a key developmental decision point. Interspecies and interploidy crosses alter when or if endosperm cellularizes, which can lead to smaller or larger seeds, or even seed abortion. Mutations in some epigenetic regulators can partially ameliorate cellularization defects. WT, Wild type.

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