Genetically modified RNAi plants - Project Genetic Engineering and the Environment

A genetically engineered RNAi-based insecticidal plant // Effects of a genetically engineered RNAi-based plant on non-target organisms →

A genetically engineered RNAi-based insecticidal plant

New genetic engineering techniques can be used to equip plants with the RNAi (RNA interference) mechanism in order to combat plant pests.
This is modelled on natural RNA interference which regulates gene activity in plants and animals. In this case, a DNA sequence has been genetically engineered to produce a specific miRNA (microRNA) that is toxic to a certain pest, such as a leaf-eating caterpillar. When the caterpillar eats this plant, it ingests the miRNA. The specific miRNA can then interfere with gene regulation in the caterpillar cells and reduce or completely block the production of essential substances. As a result, the caterpillar will die. This mechanism is called RNA interference.

The use of miRNA against pests also poses risks to other insects that are not pests – these are known as non-target organisms. If non-target organisms living on the same plant take up the miRNA, the RNAi mechanism can be triggered in these organisms and disrupt their gene regulation. This is particularly the case if there are similarities between the mRNA of pests and non-pests to which the miRNA is meant to bind.

References and further reading:
Bohle et al. 2024: Where does the EU-path on new genomic techniques lead us? https://doi.org/10.3389/fgeed.2024.1377117
Haller et al. 2019: Responses of two ladybird beetle species (Coleoptera: Coccinellidae) to dietary RNAi), https://doi.org/10.1002/ps.5370
De Schutter et al. 2022: RNAi-Based Biocontrol Products: Market Status, Regulatory Aspects, and Risk Assessment, https://doi.org/10.3389/finsc.2021.818037

Effects of a genetically engineered RNAi-based plant on non-target organisms

This is an example of a genetically engineered plant designed to produce a specific miRNA that is toxic to a pest insect (target organism). Many of the other insect species (non-target organisms) which live on and around the plant may be directly or indirectly affected. For example, if aphids feed on the plant, the miRNA may not be toxic to them, but they absorb the miRNA which can accumulate. If ladybirds subsequently eat these aphids, the miRNA can be transferred and become harmful to the insects. Whether this is actually the case depends on various factors, including the amount of miRNA ingested and similarities between the genetic material of the pest and the non-target organism.