Functional enrichment of genes harboring 10-DAP-specific and 15-DAP-specific siRNA loci within 2-kb flanking regions. a. Expression heat map of kernel-specific and endosperm-specific siRNA loci. 453 kernel-specific and 729 endosperm-specific siRNA loci were identified based on a cutoff of a five-fold difference in average siRNA abundance among the three kernel stages (0, 3, 5 DAP) and three endosperm stages (7, 10, 15 DAP), containing at least 1,000 reads combined from the 12 samples, red indicates high expression level, blue indicates low expression level. b. Expression analysis of 10-DAP-specific and 15-DAP-specific siRNA loci in the B73 and Mo17 reciprocal crosses. The siRNA abundance in 7-, 10- and 15-DAP endosperm were first normalized and then clustered based on a five-fold difference in average siRNA abundance among different endosperm developmental stages in both reciprocal crosses, and 776 and 270 stage-enriched siRNA loci in the 10- and 15-DAP endosperms were identified, respectively. c. Heatmap of 10-DAP and 15-DAP specifically expressed siRNA loci and their associated genes enriched in the GO analysis. The color scale in blue (low), while (medium), and red (high) represents the relative expression level of maternal or paternal alleles, “M” represents Mo17, “B” represents B73.DAP: days after pollination.