Towards the elements of successful insect RNAi

Abstract

RNA interference (RNAi), the sequence-specific suppression of gene expression, offers great opportunities for insect science, especially to analyze gene function, manage pest populations, and reduce disease pathogens. The accumulating body of literature on insect RNAi has revealed that the efficiency of RNAi varies between different species, the mode of RNAi delivery, and the genes being targeted. There is also variation in the duration of transcript suppression. At present, we have a limited capacity to predict the ideal experimental strategy for RNAi of a particular gene/insect because of our incomplete understanding of whether and how the RNAi signal is amplified and spread among insect cells. Consequently, development of the optimal RNAi protocols is a highly empirical process. This limitation can be relieved by systematic analysis of the molecular physiological basis of RNAi mechanisms in insects. An enhanced conceptual understanding of RNAi function in insects will facilitate the application of RNAi for dissection of gene function, and to fast-track the application of RNAi to both control pests and develop effective methods to protect beneficial insects and non-insect arthropods, particularly the honey bee (Apis mellifera) and cultured Pacific white shrimp (Litopenaeus vannamei) from viral and parasitic diseases.

Developing an in vivo toxicity assay for RNAi risk assessment in honey bees, Apis mellifera L

“…The successful use of RNAi as a pest management tool depends on the identification of target genes essential for the insect to function (e.g. housekeeping genes), genes with high mRNA turnover coding for proteins with short half-life, stability of dsRNA, and the ability to deliver sufficient amounts of dsRNA (Huvenne and Smagghe, 2010;Scott et al, 2013). The potential applications for RNAi in pest management include oral administration of dsRNA in baits (Zhou et al, 2008), embedded in nanoparticles (Zhang et al, 2010), expressed in E. coli and formulated as a biological insecticide (Zhu et al, 2011), or expressed in transgenic plants (Baum et al, 2007;Mao et al, 2007).…”

“…The general framework for risk assessments of Bt crops has been suggested as an appropriate model for assessing the risk of RNAi based technologies (CERA, 2011;Scott et al, 2013). However, in contrast to Bt crops, the potential for RNAi to cause adverse effects to non-target organisms is somewhat dependent on the gene, target sequence and the persistence of the effect (USEPA, 2014).…”

“…Early characterization suggests that the spectrum of activity is expected to be narrow and thus species taxonomically related to the target organism are more likely to be susceptible (Baum et al, 2007;Whyard et al, 2009;Bachman et al, 2013), although more empirical information is necessary (USEPA, 2014). In addition, some orders of insects seem to be inherently resilient to RNAi and are therefore unlikely to be affected (Terenius et al, 2011;Bachman et al, 2013;Scott et al, 2013).…”

Parental RNA interference of genes involved in embryonic development of the western corn rootworm, Diabrotica virgifera virgifera LeConte

“…This pathway has been implicated as a mechanism of defense against invasive nucleic acids from viruses or from mobile genetic elements, and has been conclusively shown to regulate gene expression in virtually all eukaryotic organisms (Fire, 2007;Hussain et al, 2010;Huvenne and Smagghe, 2010;Scott et al, 2013;Terenius et al, 2011).…”

Discovery of midgut genes for the RNA interference control of corn rootworm

“…The argonaute proteins of RISC cleave the target mRNA strand complementary to their bound siRNA, which determines the specificity of the RNAi activities through precise base-pairing recognition of their complementary target RNAs 14 . Many genes have been reported to be potential targets in WCR following the provision of dsRNA in diet bioassay 13,15,16 and demonstrate that WCR is sensitive to orally delivered dsRNA, providing a new management approach for this important pest 17,18 . Pest control via RNA interference has been demonstrated in planta by expressing dsRNA targeted toward the "housekeeping" genes α-tubulin, V-ATPase A 13 , and C subunit 19 or genes involved in cellular pathways such as snf7 20 .…”