Identification of imprinted genes in the maize endosperm. a. Number of maternally expressed siRNA loci (MESL) that were identified in the 7-, 10- and 15-DAP endosperm. b. Average read count of 10-DAP-specific imprinted siRNA loci in the three developing endosperm samples of the B73 and Mo17 reciprocal crosses. c. Dynamic imprinting status of imprinted siRNA loci during endosperm development. Spots clustered at the upper-right corners at 10 DAP have more than 90% maternal reads (MESLs). DAP: days after pollination.