The goal of this project is to contribute to understanding the role of genomic imprinting on the development of seeds (grains) of cultivated barley (Hordeum vulgare L.). Barley represents a diploid model species of temperate cereals whose seeds are used as feed, for malt production, and direct consumption. As in other Angiosperm species, double fertilization occurs during seed production, leading to the development of embryo and nutritive tissue called endosperm. Beyond the role of nutritive depository for the developing seed, endosperm plays a part in the control of germination and the establishment of post-zygotic interspecies and interploidy hybridization barriers. These processes are controlled by genomic imprinting, i.e., an epigenetic process in which so-called imprinted genes are transcribed only from one of the parents. Importantly, a balanced ratio of maternal and paternal factors is necessary for proper seed development. Functional analyses of genomic imprinting are almost missing in cereals, where endosperm persists as the main storage tissue for the germinating seed. Therefore, we have focused on the study of genomic imprinting in barley. In a previous project, we identified 261 imprinted genes in cultivated barley, which will be characterized using genomic data in this project. Subsequently, we will focus on the yet unknown maternally expressed (paternally imprinted) transcription factor PROLAMIN BINDING BOX (PBF) alias HIGH LYSINE 3 (LYS3), which is important for the development of barley grains and the accumulation of storage substances. For this gene, we will perform (epi)genetic analysis of genomic imprinting, evaluate the dynamics of expression in developing seeds, and identify target genes of LYS3 during early endosperm development. This project will significantly contribute to the fulfillment of the objectives of the COST CA22157 RECROP action and, in the longer term, may also help in the breeding of cereals with higher or more stable yields.