Correlation of imprinted siRNA loci and imprinted genes in maize endosperm. a. Simulated concurrence of imprinted genes and imprinted siRNA loci based on 0.1 kb, 0.5 kb, 1 kb, 2 kb, 5 kb and 10 kb. The observed number of concurrent imprinted genes and imprinted siRNAs was significantly higher than that derived from 1000-time simulation according to the hypergeometric distribution test. The peaks in each line indicate the biggest time of simulated concurrent imprinted genes and imprinted siRNAs in terms of different length of flanking regions. b. Parental expression heat map of 11 pairs of imprinted genes and imprinted siRNAs in three developing endosperm based on 2-kb criteria (expression data of two imprinted genes are unavailable).