A model system test of trophic transmission of RNA interference effects using the milkweed bug Oncopeltus fasciatus...

Designing species-specific dsRNAs makes gene knockdown by RNA interference (RNAi) ideal for pest control. Here, we establish the milkweed bug Oncopeltus fasciatus as a lab model to assess RNAi impacts. Oncopeltus are harmless, easy to rear and highly susceptible to RNAi. Knockdown of developmental regulatory genes by parental RNAi-dsRNA administered to adult females with effects observed in their offspring-is technically straightforward and even partial knockdown results in scorable, gene-specific morphological defects. Defects were detectable at low dsRNA doses and duration of effects increased with dose, exhibiting improved sensitivity over measurements of mortality. While delivery by injection is most effective, we show that Oncopeltus are susceptible to RNAi via ingestion. We tested potential passage of RNAi effects from prey to predator, exploiting Oncopeltus egg cannibalism, injecting females with dsRNA and feeding their offspring to different females never exposed to exogenous dsRNA. The offspring of this second group of females displayed gene-specific defects in similar ranges to females directly fed dsRNA. Thus, RNAi effects can be passed generationally and trophically. Although effects on non-target organisms through the food chain are possible, the subtle responses in this scenario suggest they are unlikely to be problematic for agricultural RNAi insecticides.