Parental memories shape seeds

It is ten years since imprinting was first demonstrated in Arabidopsis, following the realization, five years earlier, that some genetic controls of seed development did not conform to Mendelian inheritance. Sixteen imprinted genes have since been identified in maize and Arabidopsis and these are expressed primarily in the endosperm, which nurtures embryo development. Imprinting results from the regulation of transcriptional silencing by DNA methylation or by Polycomb Group complex-mediated histone methylation. Here we review recent studies suggesting that imprinting results from global epigenetic changes that occur during female gametogenesis. We also discuss why imprinting has evolved and what its biological functions might be.