Insecticidal and synergistic activity of dsRNAs targeting buprofezin-specific genes against the small brown planthopper, Laodelphax striatellus.

The small brown planthopper, Laodelphax striatellus, is a dangerous pest in rice fields. Although buprofezin has been used to control L. striatellus for more than a decade, the occurrence of buprofezin-resistant L. striatellus has been recently reported. To develop an alternative pest control strategy, comparative transcriptome analysis of buprofezin-treated and nontreated L. striatellus was performed to screen the buprofezin-specific target genes for RNA interference (RNAi) application. Among six genes downregulated in the buprofezin-treated L. striatellus, RNAi-based silencing of the lipophorin precursor, endocuticle structure glycoprotein, and chitin synthase significantly induced the lethality of L. striatellus in a concentration-dependent manner. In addition, a cocktail of double-stranded RNAs against these three genes showed synergistic effects with buprofezin. These results provide RNAi-based effective approaches to control L. striatellus as well as an efficient method to identify novel target genes for RNAi application.

Development of a Bacillus thuringiensis based dsRNA production platform to control sacbrood virus in Apis cerana.

BACKGROUND: Sacbrood virus (SBV) is a fatal viruses that infects the Asian honey bee, Apis cerana in Korea. Recently, RNA interference (RNAi) has been suggested as a promising strategy for the suppression of honey bee viruses. For the efficient control of SBV infection using RNAi, simple and cost-effective methods to produce double-stranded RNA (dsRNA) are needed. RESULTS: To develop a dsRNA production platform using Bacillus thuringiensis (Bt), pBTdsSBV-VP1 vector was constructed in which the SBV vp1 gene was located between two oppositely oriented cyt promoters. Both strands of the vp1 gene were bidirectionally transcribed under the control of the sporulation-dependent cyt promoter in Bt cells transformed with pBTdsSBV-VP1, and the resulting dsRNA was easily extracted from the Bt transformant, Bt 4Q7/pBTdsSBV-VP1, by inducing its autolysis. The replication of SBV was dramatically suppressed in A. cerana workers who ingested the dsRNA produced from the Bt 4Q7/pBTdsSBV-VP1. CONCLUSION: In this study, we successfully silenced SBV in its host, A. cerana, by the application of exogenous dsRNA produced from an entomopathogenic bacteria, Bt. These results suggested that Bt could be a useful dsRNA production platform to control viral pathogens in their host insects. © 2019 Society of Chemical Industry.