Fig. 7

RNA interference (RNAi) pathway members in malacostracans. a Exogenous viral dsRNA is imported into the cytoplasm and is cleaved by the endoribonuclease from the RNase III family, Dicer. Cleaved fragments of dsRNA are known as small interfering RNAs (siRNAs). Dicer contains both Piwi/Argonaute/Zwille (PAZ) and helicase domains. Dicer activates the RNA-induced silencing complex (RISC), which is comprised of Argonaute-2 and the transactivating response RNA-binding protein (TRBP). Single-stranded siRNAs are incorporated into a RISC complex, upon which the siRNAs form complementary base-pairing to target mRNA and mRNA cleavage ensues. Other RISC-associated proteins include R2D2 and Loquacious in D. melanogaster. Dicer is also involved in microRNA (miRNA) biogenesis. Encoded by the genome, miRNAs are involved in the regulation of gene expression in the RNAi pathway. Transcribed by RNA polymerase II, Pri-miRNA is a long primary transcript of miRNAs and is processed into a stem-loop containing pre-miRNA by the microprocessor complex consisting of a ribonuclease III enzyme Drosha and Pasha, which is also known as DGCR8, protein. Pre-miRNA enters the cytoplasm and is cleaved by Dicer to generate a mature miRNA that is then integrated into the RISC complex. The miRNA-targeted transcript is either degraded or silenced. Phylogenetic trees of b Dicer, c Drosha, d TRBP and e Pasha are constructed using the maximum-likelihood method from an amino acid multiple sequence alignment. Taxa labels are depicted as their respective colour codes. Bootstrap support values (n = 1000) for all trees can be found in Additional file 26: Figure S14. Scale bar represents substitution per site