Abstract
RNA interference (RNAi) effects in insects are highly variable and may be largely dependent upon the stability of introduced double-stranded RNAs to digestion by nucleases. Here, we report a systematic comparison of RNAi effects in susceptible red flour beetle (Tribolium castaneum) and recalcitrant pea aphid (Acyrthosiphon pisum) following delivery of dsRNAs of identical length targeting expression of V-type ATPase subunit E (VTE) and inhibitor of apoptosis (IAP) genes. Injection and ingestion of VTE and IAP dsRNAs resulted in up to 100% mortality of T. castaneum larvae and sustained suppression (>80%) of transcript levels. In A. pisum, injection of VTE but not IAP dsRNA resulted in up to 65% mortality and transient suppression (ca. 40%) of VTE transcript levels. Feeding aphids on VTE dsRNA reduced growth and fecundity although no evidence for gene suppression was obtained. Rapid degradation of dsRNAs by aphid salivary, haemolymph and gut nucleases contrasted with stability in T. castaneum larvae where it appears that exo-nuclease activity is responsible for relatively slow digestion of dsRNAs. This is the first study to directly compare RNAi effects and dsRNA stability in receptive and refractory insect species and provides further evidence that dsRNA susceptibility to nucleases is a key factor in determining RNAi efficiency.
Highlights
The use of RNA interference (RNAi) to suppress the expression of target genes in insects is proven as a research technique to elucidate gene function [1,2]
A systematic study has been conducted to compare RNAi effects in T. castaneum and A. pisum following the delivery of dsRNAs of identical length targeting two genes known to be critical for insect development
The control of apoptosis is vital for development and RNAi studies targeting the expression of inhibitor of apoptosis (IAP) genes have previously been reported in dipteran and hemipteran species [58,59,60]
Summary
The use of RNA interference (RNAi) to suppress the expression of target genes in insects is proven as a research technique to elucidate gene function [1,2]. Successful induction of RNAi effects through injection or feeding dsRNAs has been achieved in many insects from different orders including species belonging to Coleoptera [3,4,5,6,7,8,9,10], Hemiptera [11,12,13,14], Lepidoptera [15,16,17,18], Diptera [19], Dictyopteran [20,21,22,23], Hymenoptera [24] and Isoptera [25]. Further complexity is provided by gaps in understanding of the relative stability of dsRNAs in vivo and the mechanisms underlying gene uptake into cells
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