Silencing Multiple Crustacean Hyperglycaemic Hormone-Encoding Genes in the Redclaw Crayfish Induces Faster Molt Rates with Anomalies.

RNA interference (RNAi)-based biotechnology has been previously implemented in decapod crustaceans. Unlike traditional RNAi methodologies that investigate single gene silencing, we employed a multigene silencing approach in decapods based on chimeric double-stranded RNA (dsRNA) molecules coined 'gene blocks'. Two dsRNA constructs, each targeting three genes of the crustacean hyperglycaemic hormone (CHH) superfamily of neuropeptides, were produced: Type II construct targeting Molt-inhibiting hormone 1 (MIH1), MIH-like 1 (MIHL1), and MIHL2 isoforms and Type I construct targeting ion transport peptide (ITP; a putative hybrid of CHH and MIH) and CHH and CHH-like (CHHL) isoforms. Both constructs were injected into juvenile redclaw crayfish, , to determine the effects of multigene knockdown on molting and developmental processes. A 20-Hydroxyecdysone (20E) enzyme-linked immunosorbent assay (ELISA) and glucose assay were used to determine the effects of RNAi on molting and hemolymph glycemic activities, respectively. Multigene silencing reduced the intermolt interval by 23%. Statistically significant elevated 20E was recorded in treated intermolt individuals, consistent with the reduced intermolt interval as well as unique and abnormal phenotypes related to the molting process, which indicates a shift in 20E-induced cascade. There was no effect of RNAi treatment on hemolymph glucose level or molt increment. Through multigene silencing and subsequent annotation of gene networks, gene blocks may provide a tailored approach to investigate complex polygenic traits with RNAi in a more efficient and scalable manner.