Expression level of endo-siRNA related genes in sense and antisense direction in different tissues. Expression data is from Ling et al. , probe sets that intersect with the endo-siRNA reads are shown. Probes are ranked according to their intensities, values >400 are considered as significant expression . Expression of sense transcripts in testes (blue) and kidney (red); expression of antisense transcripts in testes repeat 1 (light green), testes repeat 2 (light violet), brain (light blue) and kidney (yellow). The entire transcriptomes of kidney sense (black), testes antisense (light grey) and kidney antisense (dark grey) were used as controls. The inset shows the curves of the average testes sample from two replicates (green), mean plus standard deviation (blue) and mean minus standard deviation (red). A representation with a fixed order of the kidney expression data and tissue dependent variations of the same gene in testes and brain results in a comparable but noisier outcome (Additional file 3: Figure S3).