Fig. 4

Secondary piRNAs sense to TEs are up-regulated after the onset of zygotic transcription. a Heatmaps show the expression levels of piRNAs sense and antisense to the 76 Tribolium TE consensus sequences from RepBase, along with the expression levels of these TEs in RNA-seq data at various developmental stages. piRNA data are normalized to the total piRNAs uniquely mapped to the genome, and RNA-seq data are normalized to the total number of reads mapping to annotated transcripts, averaged between two biological replicates. b Scatter plots show the expression of sense (right) and antisense (left) piRNAs in the maternal piRNA pool (“maternal”; pooled libraries of oocytes and 0–5-h embryos, two biological replicates each) and the post-zygotic piRNA pool (“zygotic”; pooled libraries of embryonic libraries between 8 and 144 h of development). Dashed lines indicate twofold increase. The most differentially expressed data points are labelled. c Nucleotide frequencies of piRNA reads corresponding to TEs in sense or antisense orientation from the maternal and zygotic libraries (as in b)