Ecological risk assessment of RNAi in a non-target arthropod, Folsomia candida

Genetically modified (GM) plants expressing dsRNA (in planta RNAi) targeting insect pests have been recently developed and provide a new approach to pest control in an era of ever growing insecticide resistance. By delivering plant-derived double-stranded RNAs (dsRNAs) through feeding, specific functions of targets insect pests will be compromised. By reducing the expression of Vacuolar-ATPase A (v-ATPase) protein specific to the western corn rootworm, Diabrotica virgifera virgifera, plants show significantly less root damage and substantial larval mortality. To ensure these GM-plants are environmentally friendly and agriculturally stable, assessing target specificity and non-target risk is critical for the long-term sustainability of this novel biotechnology. This study investigates whether in vitro synthesized v-ATPase dsRNA targeting D. v. virgifera can impact a soil microarthropod, Folsomia candida. Specifically, 10-day old F. candida larvae fed with an artificial yeast-agar diet that was laced with 70µg of dsRNA (~7 µg/individual), including a negative control (β-glucouronidase dsRNA; dsGUS) and two treatments (dsRNAs from F. candida and D. v. virgifera; dsFC and dsDVV). The vehicle control contained no genetic material (nuclease free water). A total of 10 replications were carried out for this dietary RNAi toxicity assay. Potential effects at the sub-organismal level were analyzed using Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR), while life history traits, including mortality/survival, growth (weight), fecundity, egg development and egg viability were used to assess the biological impact at the organismal level. Results from this study exhibited no significant effect of in vivo dsRNA treatments in F. candida in terms of gene expression and life history traits. These combined findings showed negligible impacts of dietary RNAi, suggesting the minimal environmental risk of in planta RNAi to F. candida, one of the major soil decomposers.

Keywords: RNAi, risk assessment, Folsomia candida, qRT-PCR, Life History Traits.