"I advocate focusing on a new plant’s characteristics."
Modern molecular biological methods have opened up new perspectives in plant breeding. Lying somewhere between genetic engineering and traditional methods, they could not only be used to produce plants with novel, improved characteristics – they could do so much faster that has been possible until now. But will this make the genetic engineering of plants superfluous? How are the new procedures to be classed in terms of authorisation and safety assessments? GMO Safety spoke to Prof. Bernd Müller-Röber, a molecular biologist at the University of Potsdam, about two of these methods - smart breeding and cisgenic technology.
Transgenic plants are in a difficult position in terms of public perception. By introducing genes isolated from other species, e.g. from bacteria, plants are altered in a way “that does not occur naturally” (EU Deliberate Release Directive). For this reason there are special legal requirements for transgenic plants. Their release into the environment and commercial use is permitted only if it can be demonstrated through elaborate authorisation procedures that this will not pose a risk to humans, animals or the environment.
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Plants bred using classic methods are classed as "natural" and do not have to go through any special authorisation procedures. However, new breeding methods have long since become established that take place at the molecular or cellular biology level, but which do not produce "genetically modified plants“ within the meaning of the law. Contrary to the public’s perception, from a scientific perspective the boundaries between genetic engineering and traditional breeding methods are blurred. Whether a new method is classed as being closer to genetic engineering or to traditional breeding methods has far-reaching consequences – on the legal and authorisation regulations to be complied with and on the plant’s acceptance and public perception.
GMO Safety: Prof. Müller-Röber, you are one of the authors of the study on the latest developments in plant genetic engineering that has just been published by the Berlin-Brandenburgische Akademie der Wissenschaften. The first chapter is about smart breeding – what exactly does this term refer to? Müller-Röber: Smart breeding is traditional breeding taken to a new level. In traditional breeding, two plants are crossed and you select from among the progeny those plants that have inherited the desired characteristic. These plants are selected according to phenotype, i.e. the appearance of the mature plants. For a few years now modern methods have been available that can be used to identify precisely those genes that are responsible for specific characteristics. This means that it is possible to analyse the hybrid progeny at genetic level at a very early stage to see whether the desired gene has been inherited or not. This means that breeders can screen hundreds, thousands, or even tens of thousands of plants in a short space of time and continue to cultivate only those that carry the relevant gene. This saves time and money. GMO Safety: Has this method already been successful? Are such products already on the market? Müller-Röber: Some plants are at the development stage, but it will certainly be a while before they are ready for market. The New Zealand company HortResearch has used this method to modify a commercial apple variety in such a way that it produces red rather than white fruit flesh. This is difficult using classic breeding methods with apple trees because it takes a very long time for the trees to bear fruit. With smart breeding, gene sequences are identified that code for enzymes that enable the formation of certain dyes. It is then possible to select hybrid plants that carry the relevant gene fragment. |
GMO Safety: Smart breeding is already being viewed by some critics of genetic engineering as a successor to genetic engineering. Will we no longer need genetic engineering methods in future?
Müller-Röber: Yes, we will. Smart breeding is actually traditional breeding. It’s just that screening now takes place at DNA level rather than at phenotypic level. This means that smart breeding is possible only if the gene for a desired trait is available in a crossable wild plant. This is not always the case, however. Where the aim is to modify plants so that they produce raw materials for the chemical industry, e.g. a new polymer, a key industrial enzyme or a protein used in pharmaceuticals, smart breeding is no use at all. This can only be achieved using the classic transgenic approach.
GMO Safety: Another modern approach that you mention in your study is cisgenic technology. What is the difference between cisgenic and transgenic plants?
Müller-Röber: In transgenic plants transgenes are introduced into the plant – that is genes from other organisms. These may be organisms that are crossable with the plant, but not necessarily. In extreme cases, a gene from a bacterium or even synthetic DNA is introduced. A cisgenic plant is produced using the same transformation technologies , but the DNA used is isolated from the plant in question. Before it is reintegrated into the plant genome, certain parts of it are combined. For instance, a gene sequence for a specific enzyme may be coupled with a regulatory element that controls the activity in certain cells or tissues. Using this method it is possible to cause a protein that is usually produced only in the leaf to be produced in the tuber of a cisgenic plant. In a broader sense, cisgenic technology is also about using genes from plant species that can be crossed, and not just genes from the same species. In this broader sense, even cisgenic technology is an inter-species technology, but it is restricted to the gene pool of crossable plants.
GMO Safety: Plants that contain only genes from their own species are often viewed less critically by the public than transgenic plants. Is this justified? Couldn’t these too lead to unforeseen effects?
Müller-Röber: From a scientific point of view, it is relatively unimportant where a particular gene comes from – from a bacterium or from another plant. The decisive factor is not so much the gene transfer itself and the gene sequence introduced, as the trait with which the gene transfer is connected. A gene taken from another plant – or from the same plant – and reintroduced with other regulatory elements can, like any other transgene, produce dramatic or less dramatic effects. From a scientific point of view, the use of cisgenic plants is not a means of improving biosafety. It is just another transformation method. It may be more of a psychological signal because consumers evidently find it easier to accept plant genes in plants than e.g. bacterial genes.
GMO Safety: Some scientists are in favour of treating cisgenic plants like products of conventional breeding methods when it comes to commercial authorisation procedures – even though genetic engineering methods are used to produce them. Do you share this view?
Müller-Röber: I don’t have a definitive opinion about this. I would rather be inclined to ask: in what way are we influencing the plant characteristics with classic breeding methods, and what effect does the transgenic or cisgenic approach have in comparison? And if I come to the conclusion that I can achieve the same or similar physiological change with classic breeding methods, then that should certainly be taken into account in the assessment. Of course, it is always difficult for a set of rules to cover grey zones. Until now, cisgenic plants have not been assessed at all – it is not clear whether they should be treated as transgenic plants or traditionally-bred plants. This is being discussed at international level. One could take the view that cisgenic plants possibly don’t come under the legislation for transgenic plants. But that is still under discussion and hasn’t yet been decided.
GMO Safety: In the EU legal systems the authorisation restriction depends on the technological method used to produce the plant. This means that genetically modified plants have to go through an elaborate authorisation procedure, while plants produced using modern breeding methods are not subject to any authorisation restriction, despite the fact that these too sometimes involve fundamental modifications. Is the technological focus justified?
Müller-Röber: I don’t believe it is very useful to focus on the technology. One needs to assess the product itself. Let me emphasise the point again: I believe that it’s not so much the way in which a plant is produced that matters, but rather the effect on the plant and the characteristic of the product – and here it is relatively immaterial whether a transgenic, cisgenic or other method was used. It is possible to insert a toxic gene into a plant using cisgenic technology. I would advocate focusing on the characteristic, i.e. on the thing that will ultimately end up in the field or on our plates. And that should also be communicated in public. All the technologies currently available to us can have a range of effects. Whether someone will go so far as to say that a traditionally bred plant must be assessed according to these criteria as well is another question.
GMO Safety: What are the prospects for plant genetic engineering?
Müller-Röber: In future we will also develop plants that have been produced partly through classic or smart breeding methods and which have then had another physiological or technical characteristic added using the transgenic approach. In future, technologies will probably be combined.
GMO Safety: Thank you for talking to us.
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