Temporal genomic imprinting regulates grain filling in barley
In cereals, the persistent endosperm accumulates starch and storage proteins, making their grains a major source of food and feed. Early grain development is epigenetically controlled through the parent-of-origin-specific expression of imprinted genes in the endosperm that regulate endosperm proliferation, nutrient accumulation and embryo nourishment. Imprinted genes have been identified in several major cereals, and a few have been functionally characterized. However, it is unclear how imprinted genes regulate the accumulation of storage compounds in cereal grains. Through spatiotemporal transcriptome analysis of 255 imprinted genes in barley (Hordeum vulgare), we identify endosperm transfer cells in grains as a hotspot of expression of imprinted genes. Furthermore, we show that transcription factor LYS3 dynamically regulates grain filling in barley through early expression of the maternal allele, followed by partial activation of the paternal allele.