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.
Highlights
Accepted: 5 March 2021Ground-breaking studies on corn root worm and cotton bollworm conducted over a decade ago [1,2] provided proof-of-concept for the use of RNA interference (RNAi) in insect pest control
The aphids on the water control diet produced negligible amounts of honeydew, reflecting the absence of phagostimulatory sugar. These data suggest that dsGFP at ≥0.5 μg μL−1 has an antifeedant effect on the insects, and that concentrations
The experiments were conducted on A. pisum clone SC_37 and M. persicae clone GPA, which are highly susceptible to RNAi [38,44]
Summary
Accepted: 5 March 2021Ground-breaking studies on corn root worm and cotton bollworm conducted over a decade ago [1,2] provided proof-of-concept for the use of RNA interference (RNAi) in insect pest control. RNAi, unlike most traditional insect control technologies, offers the potential for exquisite control over the specificity of control agents [6,7]. This is because the enzyme of the Argonaute family in the RNA-induced silencing complex (RISC) is a guide-dependent RNase, requiring perfect sequence complementarity between the target transcript and the 21 nt guide RNA, a small interfering RNA (siRNA) generated by Dicermediated cleavage of double-stranded RNA (dsRNA) [8]. The motivation for our research was the increasing recognition that empirical studies on the taxon specificity of RNAi are essential for the successful application of this technology to insect pest control.
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