A survey on the off-target effects of insecticidal double-stranded RNA targeting the Hvβ´COPI gene in the crop pest Henosepilachna vigintioctopunctata through RNA-seq

The specificity of the double-stranded RNA (dsRNA) used in the RNA interference (RNAi) technique is crucial for the success of sequence-specific gene silencing. Currently, RNAi-mediated insect control is a trending research topic. However, the off-target effects of the dsRNA in RNAi are a major concern. In this study, the dsHvβ´COPI (coat protein complex I, β´ subunit)-treated and untreated transcriptomes of the 28-spotted potato lady beetle (Henosepilachna vigintioctopunctata) were compared to understand its off-target gene silencing effects. The RNA-seq results revealed that 63 and 44 differentially expressed genes (DEGs) were upregulated and downregulated, respectively, in the dsHvβ´COPI treated group as compared with the control. Validation of the differential expressions of some selected DEGs via reverse transcription-quantitative PCR (RT-qPCR) analysis confirmed the reliability of the transcriptome analysis results. Further downstream analysis revealed that there were no genes homologous with Hvβ´COPI in H. vigintioctopunctata. Additionally, no genes with a >11 bp continuous match with dsHvβ´COPI were found in the H. vigintioctopunctata transcriptome. Six genes (Hvcitron, Hvhelicase, Hvtransposase, Hvserine, Hvdynein, and HvE3 ubiquitin) were selected to examine the off-target activity of dsHvβ´COPI based on their potential involvement in various H. vigintioctopunctata metabolic pathways. The severity of silencing these six off-target genes was evaluated by employing RNAi. The RNAi results confirmed the downregulation of the expression of all six genes, although there was no significant lethality. The findings of this study will be helpful in the risk analysis of future RNAi-mediated pest control experiments.