This report is the outcome of an EFSA procurement (OC/EFSA/GMO/2015/02) which aims at reviewing relevant scientific information on RNA interference (RNAi) that could serve as baseline information for the environmental risk assessment of RNAi-based genetically modified (GM) plants. The report is based on a systematic literature search on the use of RNAi molecules in arthropods, nematodes, annelids and molluscs with dsRNA, siRNA and miRNA applied primarily through feeding and soaking (oral

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... on). The numbers of retrieved publications covering these areas are reported, along with the species name, life stages tested, the target gene and its function, details of the test substances and their concentrations used, methods of delivery and effects. Separate sections discuss the available information on: (1) the uptake and systematic spread of RNAi activity, including a description of the various components involved in this process; (2) the mechanisms of dsRNA-, siRNA-and miRNA-elicited gene silencing and the different factors involved in RNAi efficiency; (3) routes of exposure of the biotic and abiotic environment to dsRNA, siRNA and miRNA from GM plants; (4) the environmental fate of dsRNA, siRNA and miRNA; and (5) the various factors that may limit non-target effects including exposure, factors influencing the silencing efficiency of dsRNA, siRNA and miRNA, possible unintended and off-target effects, and their mechanisms. Finally, an overview of the species of arthropods, nematodes, annelids and molluscs for which genomic data are available is also presented. The report identifies some of the challenges involved in developing plants with RNAi systems which affect invertebrate gene expression. The report also concludes that, currently, knowledge on issues such as exposure, specificity, offtarget effects, sequence similarities and bioinformatics is very limited, as only a few RNAi expressing plants which specifically target invertebrate species have been developed and comprehensively studied.