New study points to unintended effects of gene editing in plants and potential negative effects on ecosystems

Gene editing causes drastic unwanted effects in gene-edited plants including severe deformities, a new scientific publication in the journal Environmental Sciences Europe shows. This is the case even when the changes are intended by the gene editor to be small tweaks to existing genes rather than, for example, the introduction of new genetic material.

More broadly, the study provides an overview of the negative effects on ecosystems that can result from the release of gene-edited plants. These unintended effects result from the intended changes induced by genome editing, which can affect various metabolic processes in the plants.

The study, authored by Dr Katharina Kawall, uses the example of camelina (Camelina sativa), a plant that is rich in polyunsaturated fatty acids. Gene editors used a CRISPR/Cas application to increase the amount of oleic acid in the camelina seeds and to reduce the amount of easily oxidised fatty acids. This was intended to extend the shelf life of the oil extracted from the camelina.

Drastic developmental defects in gene-edited camelina

The new paper reviews previous research in CRISPR-edited camelina lines engineered to have an altered fatty acid profile. Unintended mutations were identified and the plants showed "drastic developmental defects" – including impaired growth, twisted leaves, and delayed bolting. Dr Kawall comments that this shows "the importance of a well-balanced fatty acid profile for the development of the plants".

Dr Kawall observes that these phenotypic defects were even more severe in a recently conducted field trial of a gene-edited camelina by Rothamsted Research in the UK. Although the crop generated the intended high oleic acid seed oil, the plants showed "very significant growth defects" in that they were "severely dwarfed".

GMWatch notes that the observed growth and developmental defects of the gene edited camelina could be arising from an altered pattern of gene function caused by unintended mutations to genes at both off-target an on-target genome editing sites. This is an outcome that was not considered by the developers.

In spite of this unexpected outcome, the authors of the paper that reported it – Johnathan Napier from Rothamsted and Jean-Denis Faure from INRA in France – actually complained in their paper about the "enormous burden" that the EU's GMO regulations place "on researchers (public or private) trying to convert their ideas into innovations and impactful outcomes".

The Napier/Faure paper also reports another gene-edited line that didn't show these deformities, but it's not clear whether they had other, less visible problems – i.e. if they were normal looking plants but with alterations in composition that could lead to unexpected toxicity and allergenicity. As far as we know, Rothamsted has never seen fit to subject their GM plants to safety tests.

"Small" changes produce big effects

The key point about the deformed camelina plants is that only small changes – gene knockouts in existing genes – were intended by the gene editors. This type of gene editing is known as an SDN-1 application and is being targeted for deregulation all over the world, including in the EU and the UK.

Camelina has a six-fold set of chromosomes and is therefore a good example to demonstrate that even small changes in the genome created with CRISPR/Cas can have a huge effect. This type of gene scissors was used to simultaneously mutate and destroy the function of ("knock out") 18 gene copies in the genome of the camelina and thus generate plants with a higher oleic acid content. Such interventions have until now hardly, or not at all, been possible with conventional breeding methods and can give rise to completely new biological properties. In the USA, these plants have already been deregulated without undergoing thorough risk assessment.

But Dr Kawall's analysis shows that even in SDN-1 applications, "major changes of plant physiology and/or phenotype become possible. In addition, there is evidently potential of disrupting metabolic pathways in the genome-edited plants causing pleiotropic effects" – effects other than those intended from the genetic modification.

Risks not dependent on introduction of foreign genes

A recent EFSA opinion also comes to the conclusion that plants with complex genetic changes need to undergo risk assessment, even in cases like this where no additional genes are inserted.

Dr Kawall's paper makes clear that gene-editing applications – most of which use CRISPR/Cas gene scissors to cut the DNA double helix to produce what is known as a “double-strand DNA break” in the genome of the targeted organism – can increase the possibilities and speed with which the genetic makeup of plants can be changed.

It does not matter whether or not additional genes are integrated into the genome – even small genetic changes induced several times in single or multiple genes, and in combination to generate novel properties, can significantly change metabolic pathways and biochemical composition.

Consequently, genetically engineered plants must undergo risk assessment even if no additional genes are inserted.

Ecosystem effects

The new paper also describes how unintended effects on ecosystem processes can occur – for example, effects on the formation of certain messenger substances, with which plants communicate and "warn" of a pest infestation. A change in the composition of fatty acids can affect and influence existing food webs. In addition, gene-edited plants could hybridise with wild species, leading to unintended effects in subsequent generations. At the same time, the gene-edited camelina has the potential to persist in the environment and spread uncontrollably. 

The paper shows that even when the gene editor intends only to make small changes through gene editing that do not involve introducing foreign genes, drastic unintended effects can result.

Source for comments on ecosystem effects: Testbiotech
https://www.testbiotech.org/en/news/genome-edited-plants-negative-effects-ecosystems-are-possible

Further information:

The new publication https://enveurope.springeropen.com/articles/10.1186/s12302-021-00482-2

The Project Genetic Engineering and the Environment (FGU) website https://fachstelle-gentechnik-umwelt.de/en/home/

Testbiotech news about a recent EFSA opinion https://www.testbiotech.org/en/press-release/efsa-risk-assessment-new-ge-plants-necessary-even-if-no-additional-genes-are-inserted