Genome demethylation and imprinting in the endosperm

Imprinting occurs in the endosperm of flowering plants. The endosperm, a product of central cell fertilization, is critical for embryo and seed development. Imprinting in the endosperm is mainly due to the inherited differences in gamete epigenetic composition. Studies have also shown that there are differences in genomic DNA methylation patterns between embryo and endosperm. Examining those differences, along with mutations in the DNA demethylase gene DEMETER, gives insight into the number of imprinted genes and how an antagonistic relationship between TE defense and gene regulation could evolutionarily affect imprinting establishment. Finally, studies demonstrate that DEMETER demethylase activity influences endosperm chromatin composition, and could possibly enhance DNA de novo methylation activity.

► Imprinting is mainly due to inherited epigenetic differences between gametes.
► Transposable elements in the endosperm are hypomethylated compared to the embryo.
► A group of endosperm siRNAs is imprinted, expressing maternally.
► Endosperm demethylation might influence siRNA production and action.
► Both PRC2 and DNA demethylation influence chromatin structure and imprinting.