The Study of Cell-Penetrating Peptides to Deliver dsRNA and siRNA by Feeding in the Desert Locust, Schistocerca gregaria

RNA(i) interference is a gene silencing mechanism triggered by double-stranded (ds)RNA, which promises to contribute to species-specific insect pest control strategies. The first step toward the application of RNAi as an insecticide is to enable efficient gene silencing upon dsRNA oral delivery. The desert locust, Schistocerca gregaria is a devastating agricultural pest. While this species is responsive to dsRNA delivered by intra-hemocoelic injection, it is refractory to orally delivered dsRNA. In this study, we evaluated the capacity of five cell-penetrating peptides (CPPs) to bind long dsRNA and protect it from the locust midgut environment. We then selected the CPP EB1 for further in vivo studies. EB1:dsRNA complexes failed to induce RNAi by feeding. Interestingly, we observed that intra-hemocoelic injection of small-interfering (si)RNAs does not result in a silencing response, but that this response can be obtained by injecting EB1:siRNA complexes. EB1 also protected siRNAs from midgut degradation activity. However, EB1:siRNA complexes failed as well in triggering RNAi when fed. Our findings highlight the complexity of the dsRNA/siRNA-triggered RNAi in this species and emphasize the multifactorial nature of the RNAi response in insects. Our study also stresses the importance of in vivo studies when it comes to dsRNA/siRNA delivery systems.

RNAi-Based Biopesticides Against 28-Spotted Ladybeetle Henosepilachna vigintioctopunctata Does Not Harm the Insect Predator Propylea japonica

RNA interference (RNAi)-mediated control of the notorious pest Henosepilachna vigintioctopunctata is an emerging environment friendly research area. However, the characterization of key target genes in H. vigintioctopunctata is crucial for this. Additionally, assessing the risk of RNAi to nontarget organisms (NTOs) is necessary for environmental safety. In this study, the potential of RNAi technology in controlling H. vigintioctopunctata infestation has been investigated by the oral delivery of double-stranded RNA (dsRNA). The results revealed that the silencing of six genes, including HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k, was highly lethal to H. vigintioctopunctata. The LC50 values of the dsRNAs used to silence these six genes were found to be less than 13 ng/μL. Moreover, the use of the bacterially expressed dsRNAs caused high mortality in the lab and field populations of H. vigintioctopunctata. Further, administration of HvHel25E and HvSrp54k dsRNAs in the predatory lady beetle Propylea japonica confirmed no transcriptional or organismal levels effects. This risk-assessment result ensured no off-target RNAi effects on the NTOs. Overall, the findings of the study suggested that HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k can be novel promising molecular targets with high specificity for H. vigintioctopunctata management with negligible effects on the NTOs.