The Arabidopsis endosperm is an unique tissue to angiosperms, and is the main tissue where imprinting occurs. Using high-throughput sequencing we found 123 new imprinted genes and expect that the total number of imprinted genes present in the endosperm ranges from 200-500. From the 114 maternally expressed imprinted genes we found 29 genes which expression mechanism are controlled by DNA methylation and/or PcG activity. For the rest of imprinted genes and presumably the majority of p4-siRNAs, the maternal expression may be controlled by other mechanisms or use homolog of known imprinting proteins
