Apr 12, 2007
“The new findings have yet to be incorporated into the risk assessment of transgenic plants.”
Katja Moch , Öko-Institut Freiburg, is the author of the expert paper “Epigenetische Effekte bei transgenen Pflanzen: Auswirkungen auf die Risikobewertung”
(Epigenetic effects in transgenic plants: impacts on risk assessment) commissioned by the German Federal Agency for Nature Conservation (BfN).
Epigenetics: New findings – new uncertainty concerning genetically modified plants?
Questions for Katja Moch
GMO Safety: The “epigenetic effects” scenario is receiving a lot of attention in the discussion about potential risks of transgenic plants. What lies behind this catchword?
Katja Moch: The Greek word epi means “on” or “over” and it refers to processes that are above genetics and not directly coded for by DNA. Traditionally, epigenetic effects refer primarily to DNA modifications which cause genes to be switched on or off or adjust the strength of expression upwards or downwards. Epigenetics is, however, increasingly also used to describe the complexity of gene regulation – the complex process through which a phenotype is produced from a genotype. Outside signals, i.e. signals from the environment, also play a part in this.
In genetic engineering, epigenetic effects describe unintended effects, since inserting gene constructs into an organism’s existing genome not only produces the desired modification, but can also interfere with gene regulatory processes and structures. However, I do not find that epigenetic effects have received much attention so far because there has been no systematic research into unintended effects and their causes. If you look at published studies, the research questions are usually very narrowly defined and do not allow for any analysis of unintended effects.
GMO Safety: Not all that long ago it was assumed that a gene coded for just one protein. Now we are aware of a whole range of mechanisms that are increasingly casting doubt on the general applicability of the old “one gene one protein” rule. To what extent are new findings from epigenetics already being incorporated into plant research and plant breeding?
Katja Moch: Your questions refer to the expert report on “Epigenetic effects in transgenic plants: impacts on risk assessment” that we produced for the Federal Agency for Nature Conservation (BfN). In this report we looked primarily at the results that are available on unintended epigenetic effects in genetically modified plants – effects that go beyond unintentional modifications at genetic level, such as multiple insertions, rearrangements, deletions, filler DNA etc. The report presents an initial summary of epigenetic effects in transgenic plants. We then looked at the implications for risk assessment and compared to see whether they are covered by the current risk assessment methods.
To your question: The new findings have been incorporated into plant genetic engineering only to a limited extent – people continue to assume that the gene construct that is inserted into plants produces only the desired characteristic over the long term. This means that the “one gene one protein” assumption still persists. However, since the transgenic constructs are inserted into the plant genome at random, genetic and epigenetic regulatory networks can be destroyed or altered.
GMO Safety: Have genetic engineering methods been refined on the basis of the new findings?
Katja Moch: Since not everything that is researched is published, I am not able to judge the situation in its entirety. In the case of genetic engineering work on plants intended for commercial applications, people take care that where possible only one copy of the gene construct is present in the plant genome. This lowers the probability of the transgene being silenced. This can be achieved by back-crossing with a non-transgenic parent line. The cell culture stage is also frequently bypassed or cut short in genetic modifications because cell culture can trigger changes at the genetic and epigenetic levels. These are both strategies for minimising unintended effects, but are primarily used to ensure that the transgenic trait is expressed in as stable a manner as possible.
GMO Safety: Epigenetic processes manifest themselves in altered plant characteristics, e.g. changes to the morphology, agronomic characteristics or plant substances. Do such effects go unnoticed in the numerous tests and inspections that transgenic lines pass through before they are authorised? Are there gaps in the current risk assessment concept?
Katja Moch: Yes, there are gaps in the current risk assessments. The greatest failing is that there are no minimum guidelines as to which methods or set of methods should be used. For instance, it is not mandatory to carry out DNA sequencing of the whole transgene insert, i.e. sequencing after the genetic modification. In general, more extensive analyses need to be introduced in the EU before authorisation. The precautionary principle should be reflected on the one hand in the number of analyses and on the other in careful assessment where differences are identified between the transgenic plant and the reference plants. After all, the evaluation of the results is a normative step in risk assessment.
Epigenetic effects that result in changes to the morphology or poorer agronomic characteristics are the easiest to identify. Things become more difficult where unknown proteins or secondary metabolites are produced or where the plant’s ability to adapt or its reaction to altered environmental conditions is affected. Concentrated, systematic research is being conducted to investigate substances contained in transgenic plants, but it is not yet ready to be used in authorisation procedures. It is also difficult to assess cases in which significant differences are found between the substances contained in the transgenic plants and those of the reference plants. In these cases further investigations are necessary to discover the relevance of the finding.
GMO Safety: Epigenetic effects are not restricted to transgenic plants. They also occur in conventionally bred plants. In other words, progeny can have characteristics that are not directly derived from those of the parents. How does the plant breeder deal with this?
Katja Moch: This is a question that goes far beyond the scope of the expert report and we are not plant breeders ourselves. In general, plant breeding depends on the type of crop. Breeding is always a process in which new variations are formed from different parent lines or populations which are then selected on the basis of desired traits. A certain degree of uniformity must be achieved for a variety. Since plant breeding – particularly when it involves marker-based selection – focuses primarily on genetic endowment, little will be generally known about epigenetic effects. What interests me concerning epigenetic effects in breeding research is the extent to which local environmental factors uniquely shape varieties or cultivars over the long term.
GMO Safety: How do you think the new findings should be used in developing new breeds – both conventional and transgenic?
Katja Moch: Your question implies that genetic modification is a breeding method – something I do not entirely agree with. Genetic modification represents an intervention that is qualitatively different from classic breeding. This is after all reflected in European legislation, which has separate regulations for genetically modified plants to regulate their special authorisation. My personal opinion is that new breeds should keep sight of local adaptations, so that the diversity of varieties used is as wide as possible and we do not end up with standardised varieties.
GMO Safety: Thank you