To control pests without pesticides, genetically modified organisms of the same species could be used. The latter carry a gene that is passed on with above-average frequency via sexual reproduction. This gene possesses traits that directly weaken the pest, or prevent pathogens from being transmitted. But how can the environmental impact of such gene-drive elements be recorded and assessed? Experts from Agroscope have authored a concept study on this topic.
The use of genetically modified insects with gene drives for purposes of pest control is now the subject of international debate (see below). This method could represent an attractive new approach for controlling pests efficiently, even without pesticides. Before such organisms are released, it is imperative to clarify their possible impact on the environment. In particular, care must be taken not to damage biodiversity.
Only, how do we do this? Agroscope is now demonstrating that experience gained with established technologies involving the release of living organisms can be used in this connection. One of these technologies is the classical biological pest-control method.
Controlling pest populations with gene drives
In sexual reproduction, half of the genetic material of each parent is passed on. In normal circumstances, therefore, each gene is transferred to half of the offspring. Gene-drive elements ensure that these genes are inherited by many more offspring than is normally the case. This enables higher levels of certain traits to be introduced into a population. This even applies for traits that are disadvantageous for the organisms in question.
But how does this work, and what do gene drives achieve? Using molecular-biological methods, insects can be genetically engineered in the laboratory to carry a gene-drive element. Used correctly, the technology can permanently modify an insect population, resulting in an insect no longer being able to transmit a pathogen, or in the reduction – or even the local eradication – of a pest population.
Testing environmental impact
Major concerns were expressed with regard to the possible environmental impact of this technology: on the one hand, because such insects would be created with the aid of genetic engineering, and then released; one the other, because gene drives could potentially lead to the global eradication of a species. In addition, it is feared that the gene-drive elements could also be transmitted to other insect species and cause damage to their populations.
The question is therefore how we can test the environmental impact in a risk assessment before such organisms are released.
Jörg Romeis and Jana Collatz from Agroscope’s Biosafety Research Group pursued this question, together with experts from the National Institute of Public Health and the Environment in the Netherlands and the University of Oxford in Britain. In an article just published in the journal Environmental Science & Policy, they demonstrate that gene-drive technology does not pose any fundamentally new environmental risks compared to established pest-control methods that are also based on the release of living organisms (see below). With these methods too, the released organisms can become established and spread. The environmental assessment of insects with gene drives can therefore build on the experience acquired with the established methods.
What are gene drives?
Gene drives are ‘selfish’ genetic elements which in sexually reproducing organisms lead to certain genes being passed on to progeny much more frequently than usual. Such gene-drive elements occur naturally. New molecular processes make it possible to artificially insert gene drives into an organism. If attached to a gene responsible for a specific trait, this trait can be ‘driven’ into a population within just a few generations. This even works if the trait involves a disadvantage for the organisms.
The technology can be used to cause the collapse of an insect population, or to modify a population in a particular direction. Mosquitoes, for example, can be modified so that they are unable to serve as hosts for the malaria pathogen.
In order for such artificial gene drives to function, the organisms in question must reproduce sexually and have a short generation time. Both preconditions are met in the case of most insects.
Stablished pest-control methods
Classical biological pest control involves the release of natural antagonists from the region of origin of an exotic pest with a view to their naturalisation in the new environment.
With sterile insect technology, the pest population is flooded with masses of infertile laboratory-bred conspecifics. As a consequence, mating no longer leads to any viable offspring. Sterilisation is effected via X-rays or with the help of genetic engineering.
Romeis J, Collatz J, Glandorf DCM, Bonsall MB (2020). The value of existing regulatory frameworks for the environmental risk assessment of agricultural pest control using gene drives. Environmental Science & Policy 108, 19-36, https://doi.org/10.1016/j.envsci.2020.02.016