Improving RNA interference in the southern green stink bug, Nezara viridula

The southern green stink bug, Nezara viridula, is a worldwide pest of many important crops. RNA from N. viridula nymphs and adults was sequenced and assembled into a transcriptome. Orthologs of genes coding for proteins involved in RNA interference (RNAi) pathways and potential target genes for RNAi-mediated control of this pest were identified by searching the transcriptome. The watery saliva, lumen and hemolymph collected from N. viridula showed lower dsRNase activity than that in the lumen and hemolymph collected from the fall armyworm, Spodoptera frugiperda , which is refractory to RNAi. Seven housekeeping genes, 60S RP L12, 40S RP S17, 18S rRNA, EF1-α, Actin, Ubiquitin and β-Tubulin , were evaluated across developmental stages and dsRNA treatments and identified 60S RP L12 and 40S RP S17 as the best reference genes for use in reverse transcriptase quantitative PCR (RT-qPCR). One microgram of dsRNA targeting the orthologs of seven known RNAi target genes ( SNF7, IAP1, IAP2, IAP5, PP1, GPCR and ATPase1 ) was tested in N. viridula . Three out of seven dsRNAs tested induced 67–100% mortality. Injection of dsRNA targeting SNF7 into N. viridula adults caused 100% mortality, while feeding dsSNF7 induced 60% mortality in both adults and nymphs. Delivery of dsRNA by either feeding or injection efficiently knocked down target gene expression. These data demonstrate that RNAi pathway components are present in N. viridula and delivering dsRNA by either injection or feeding induces silencing of target gene expression and mortality, suggesting that RNAi-based methods could be developed to manage this pest.