Antiviral RNAi is preserved in dsRNA-resistant Colorado potato beetle (Leptinotarsa decemlineata)

Biocontrol strategies based on RNA interference (RNAi) hold great potential against the Colorado potato beetle (Leptinotarsa decemlineata), but the emergence of dsRNA-resistant populations threatens their sustained efficacy. In insects, RNAi constitutes a major antiviral defense mechanism, primarily through the production of virus-derived small interfering RNAs (vsiRNAs) and, in certain species, PIWI-interacting RNAs (vpiRNAs). Certain viruses can muffle this response by expressing viral suppressors of RNAi (VSRs). We hypothesized that viruses encoding VSRs may contribute to the high resistance levels to dsRNA reported in a population of L. decemlineata (CEAS 300). In testing this hypothesis, we first characterized the virome of two susceptible and the dsRNA-resistant CEAS 300 L. decemlineata populations and identified eight novel RNA viruses. Comparative analysis revealed no association between RNA virus abundance and incidence among the populations and the dsRNA resistance phenotype. Small RNA profiling revealed a combination of vsiRNAs (widespread) and vpiRNAs (against a single virus) in all three L. decemlineata populations, confirming that the antiviral RNAi machinery remains active in the dsRNA-resistant population and that resistance is not due to defects in core RNAi components. Conversely, dsRNA treatment affected the abundance and vsiRNA response to one virus, and these effects were predominantly observed in the dsRNA-resistant population. Overall, our findings provide new insights into resistance to RNAi and host-virus interactions, highlighting the relevance of RNA viruses in the context of RNAi-based pest control strategies.