GSE22892
Deep sequencing of organ- and stage-specific microRNAs in the evolutionarily basal insect Blattella germanica (L.) (Dictyoptera, Blattellidae)
microRNAs (miRNAs) have been reported as key regulators in the post-transcriptional process in eukaryotic cells. In insects most of the studies have been reported in holometabolans while only recently two hemimetabolans  (Locusta migratoria and Acyrthosiphonpisum) have had their miRNAs identified. Therefore, the study on miRNAs of the evolutionarily basal hemimetabolan  Blattella germanica, may provide valuable insights on the structural and functional evolution of miRNAs. Small RNA libraries of the cockroach B. germanica were built from the whole body of the last instar nymph, and the adult ovaries. The high throughput Solexa sequencing resulted in approximately 11 and 8 million reads for the whole-body and ovaries, respectively. Bioinformatic analyses identified 38 known miRNAs as well as 11 known miRNA*s. We also found 411 miRNA candidates conserved in other insects and 1017 candidates specific of B. germanica. The positive correlation between Solexa data and real-time quantitative PCR showed that reads can be used as quantitative method. Novel miRNA candidates were validated by decreasing levels of expression in dicer-1 RNAi knockdown individuals. The comparison of the two libraries indicates that whole-body nymph contain more known miRNAs than ovaries, whereas the adult ovaries are enriched with novel miRNA candidates. Our study has identified many known miRNAs and novel miRNA candidates in the basal hemimetabolan insect B. germanica, and most of the specific sequences were found in ovaries. Deep sequencing data reflect miRNA abundance and Dicer-1 RNAi assay is a reliable method to validate novel miRNAs. Overall design: Small RNAs were sequenced whole body of the last instar nymph and adult ovaries of the cockroach Blattella germanica.