Non-Target Effects of dsRNA Molecules in Hemipteran Insects

Abstract

Insect pest control by RNA interference (RNAi)-mediated gene expression knockdown can be undermined by many factors, including small sequence differences between double-stranded RNA (dsRNA) and the target gene. It can also be compromised by effects that are independent of the dsRNA sequence on non-target organisms (known as sequence-non-specific effects). This study investigated the species-specificity of RNAi in plant sap-feeding hemipteran pests. We first demonstrated sequence-non-specific suppression of aphid feeding by dsRNA at dietary concentrations ≥0.5 µg µL−1. Then we quantified the expression of NUC (nuclease) genes in insects administered homologous dsRNA (with perfect sequence identity to the target species) or heterologous dsRNA (generated against a related gene of non-identical sequence in a different insect species). For the aphids Acyrthosiphon pisum and Myzus persicae, significantly reduced NUC expression was obtained with the homologous but not heterologous dsRNA at 0.2 µg µL−1, despite high dsNUC sequence identity. Follow-up experiments demonstrated significantly reduced expression of NUC genes in the whitefly Bemisia tabaci and mealybug Planococcus maritimus administered homologous dsNUCs, but not heterologous aphid dsNUCs. Our demonstration of inefficient expression knockdown by heterologous dsRNA in these insects suggests that maximal dsRNA sequence identity is required for RNAi targeting of related pest species, and that heterologous dsRNAs at appropriate concentrations may not be a major risk to non-target sap-feeding hemipterans.

Assessing the Functionality of RNA Interference (RNAi) in the Phloem-feeding Maize pestDalbulus maidis

“…As molecular methods improve, more studies are reporting successful oral delivery of dsRNA molecules overcoming the known hemipteran cellular barriers against RNAi (Ghosh et al, 2018;Jain et al, 2021;Sharma et al, 2021). Evidence of successful RNAi mechanism induced by oral delivery of dsRNA was recently presented in Pseudococcus maritimus, the grape mealybug (Arora et al, 2021). As in our study, RNAi silencing was evident in P. maritimus as early as 3days when insects were fed dsRNA complements of osmoregulation genes (aquaporin (AQP) and a sucrase (SUC)) (Arora et al 2020).…”

RNAi-Based Biocontrol Products: Market Status, Regulatory Aspects, and Risk Assessment

“…When dsRNA is administered at high concentrations, it could theoretically saturate the core RNAi machinery (42). Since RNAi is a part of the antiviral immunity of the cell, such a saturation could have a substantial impact on the defense of the cell against viruses (43)(44)(45). While in mice, saturation of the RNAi machinery was found to cause lethality (46), this has not yet been reported in arthropods (39).…”

Current Scenario of Exogenously Induced RNAi for Lepidopteran Agricultural Pest Control: From dsRNA Design to Topical Application

“…Other aspects to consider for commercial application of RNAi are cost-efficiency, safety, the delivery to the site of action in the target organism and adverse effects in NTOs. The exposure of NTO is dependent on several parameters, including application rate, timing of application, application method, number of applications, off-site movement of the dsRNA, and stability and persistence of the dsRNA [181,182].…”