Abstract
The voltage-gated sodium ion channel (VGSC) belongs to the largest superfamily of ion channels. Since VGSCs play key roles in physiological processes they are major targets for effective insecticides. RNA interference (RNAi) is widely used to analyse gene function, but recently, it has shown potential to contribute to novel strategies for selectively controlling agricultural insect pests. The current study evaluates the delivery of dsRNA targeted to the sodium ion channel paralytic A (TcNav) gene in Tribolium castaneum as a viable means of controlling this insect pest. Delivery of TcNav dsRNA caused severe developmental arrest with larval mortalities up to 73% post injection of dsRNA. Injected larvae showed significant (p < 0.05) knockdown in gene expression between 30–60%. Expression was also significantly (p < 0.05) reduced in pupae following injection causing 30% and 42% knockdown for early and late pupal stages, respectively. Oral delivery of dsRNA caused dose-dependant mortalities of between 19 and 51.34%; this was accompanied by significant (p < 0.05) knockdown in gene expression following 3 days of continuous feeding. The majority of larvae injected with, or fed, dsRNA died during the final larval stage prior to pupation. This work provides evidence of a viable RNAi-based strategy for insect control.
Highlights
The voltage-gated sodium ion channel (VGSC) belongs to the largest superfamily of ion channels
The results provide proof of concept for this approach to be used in the sustainable control of insect pests, since this strategy is both highly specific and effective towards the targeted species, and is unlikely to effect beneficial insects such as pollinators and those involved in biological control, as there is no homology between the double-stranded RNA (dsRNA) fragment and off target sequences
Homology of the TcNav dsRNA fragment designed by the E-RNA interference (RNAi) web tool to the other 744 insect Nav sequences, including representatives from important pollinator species, held by NCBI was investigated using the MegaBLAST algorithm
Summary
468 bp efficacy but demonstrate higher specificity. The use of a molecular approach such as RNA interference provides a platform enabling a highly specific and targeted strategy to insect control. RNA interference (RNAi) represents a unique form of post-transcriptional gene silencing (PTGS); it is a recognized cellular mechanism for defence against viral invasion and post-transcriptional regulation of mRNA19 It is the specific downregulation of gene expression mediated by an artificial double-stranded RNA (dsRNA) molecule where one strand of the dsRNA corresponds to part or all of a specific gene transcript[20]. RNAi-based gene silencing has the potential to represent a novel insecticide technology, since it is theoretically possible to protect plants against insects by down regulating the expression of essential genes in the pest[20,29,30,31] This technology should allow non-conserved sequences to be targeted, conferring a high degree of specificity. The results provide proof of concept for this approach to be used in the sustainable control of insect pests, since this strategy is both highly specific and effective towards the targeted species, and is unlikely to effect beneficial insects such as pollinators and those involved in biological control, as there is no homology between the dsRNA fragment and off target sequences
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