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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGICALLY BASED PEST MANAGEMENT IN MODERN CROPPING SYSTEMS

Location: North Central Agricultural Research Laboratory

Title: RNAi-based insecticidal crops: potential effects on non-target species

Authors
item Lundgren, Jonathan
item Duan, Jian

Submitted to: Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2013
Publication Date: August 2, 2013
Citation: Lundgren, J.G., Duan, J.J. 2013. RNAi-based insecticidal crops: potential effects on non-target species. Bioscience. 63(8): 657-665.

Interpretive Summary: Genetically modified (GM) crops currently manage insect pests by expressing insecticides derived from the insect disease, Bacillus thuringiensis (Bt). The next generation of GM insecticidal crops will express interference RNA (RNAi). RNAi is used by many eukaryotic organisms to regulate gene expression and resist genetic invaders like viruses and transposons. Essentially, small fragments of RNA bind to messenger RNA produced by the target organism, and block gene expression. RNAi-based GM crops will use small RNAs to block critical gene function in insect pests, thereby killing them. Potential pitfalls posed by RNAi-based crops that have not been investigated including effects on non target organisms within the environment where GM crops are grown. The unique characteristics of RNAi and critical knowledge gaps preclude our ability to predict the ecological consequences of this new technology. Research is uncovering that small RNAs can bind to many off-target places on a genome, and inadvertently block gene expression. Specific areas that warrant future work include 1) The persistence of small RNAs associated with GM plants in the environment is largely unknown, 2) There is poor resolution of crop-based food webs and additional information regarding which species will be exposed to RNAi-based crops is needed, 3) Genomic information for most species is absent and limits our ability to understand which species may be affected by RNAi, and 4) It is unclear whether laboratory testing that only focuses on toxicity can predict the effects of sublethal gene silencing produced by RNAi. Balancing the benefits of RNAi-based technologies against its environmental effects will ensure that this valuable technique is preserved for the future.

Technical Abstract: RNAi is a sequence specific mechanism that silences protein production when particular mRNAs are bound and enzymatically cleaved. Genetically modified crops that silence critical gene function in insect pests have been developed, and are a likely future direction for commercial pest management. Potential pitfalls posed by RNAi-based crops include 1) silencing the target gene in non-target organisms, 2) off-target gene silencing, 3) immune stimulation, and 4) saturation of the RNAi machinery. Although steps can be taken to reduce the likelihood of accidental binding of small RNAs to unintended gene targets, published evidence suggests that off-target and non-target binding and gene suppression may be more widespread in RNAi than was previously believed. Furthermore, the widespread adoption of currently available GM crops suggests that the number of species that will be exposed to RNAi-based GM crops will be extensive, although their degree of exposure and risk requires additional research. Specific areas that warrant future work include 1) The persistence of small RNAs associated with GM plants in the environment is largely unknown, 2) There is poor resolution of crop-based food webs and additional information regarding which species will be exposed to RNAi-based crops is needed, 3) Genomic information for most species is absent and limits our ability to understand which species may be affected by RNAi, and 4) It is unclear whether laboratory testing that only focuses on toxicity can predict the effects of sublethal gene silencing produced by RNAi. Ultimately, the costs and benefits of pesticidal RNA must be considered relative to current pest management options.

Last Modified: 8/30/2014
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