What is genetic engineering? A plea for a rational definition of what it is and what it isn’t

The public debate on genetic engineering in agriculture is largely characterised by misinformation, myths and a confused understanding of nature, writes Professor Hans-Jörg Jacobsen (PhD).

Professor Hans-Jörg Jacobsen (PhD) was head of the plant biotechnology department at the Institute of Plant Genetics at Leibniz Universität Hannover until 2015, as well as a visiting professor at the Biology department of the Northeastern University in Boston between 2000 and 2017. He is a contributor to international journals in the field of plant sciences.

Our level of knowledge today is completely different from 30 years ago when the current legislation on genetic engineering was drawn up. It must thus be thoroughly revised and adapted to the current state of knowledge. If Europe does not want to be a loser in global competition, this must also be done quickly.

Where does the diversity of plant varieties come from?

Random spontaneous mutations are the basis of evolution and biodiversity. They have determined the slow pace of plant breeding over the past 10,000 years, and scientific breeding was not developed until around 1903. Landraces became our present-day high yielding varieties [1]: ‘Induced’ mutations replaced spontaneous mutations, for which ionising radiation or mutagenic chemicals were used (so-called ‘guided evolution’). We have known for a long time that, in addition to the spontaneous or induced mutations in the genes, chromosome breaks or alterations can also occur in the number of chromosomes. These change the genetic material randomly and accidentally, with effects that usually turn out negative.

Today, induced mutations are found in almost all cultivated plants, including varieties of organic farming. It has never been detected during variety registration tests that varieties created by induced mutations carry any risks. And when genetic engineering legislation was drafted at the end of the 1980s, spontaneous or induced mutations were exempted from regulation. At that time, the reason given for this decision was “that one has many years of experience” with these mutants (at the time it was 30 years).

Genetic flexibility of plants

Another aspect plays an important role in our plants: pollen – for example in cross-pollinated species – is mobile, which means that it can land somewhere and fertilise a flower. If the genomes are compatible, then a new species can emerge – for example, rapeseed, which is a natural cross between a wild cabbage and the rapeseed plant. If the genomes are not compatible, the newly created hybrids often resort to a genetic trick: they duplicate the respective genomes, which thus enables the formation of fertile germ cells. In our wheat, this has even happened twice: first two kinds of grass merged, giving the tetraploid durum-wheat, then a third genome was added from another grass, and our hexaploid cultivated wheat was ready. In other words, three genomes created a new species. From this, we can learn that Mother Nature does not respect our man-made definitions of what constitutes a species and what does not. She also crosses boundaries and is constantly evolving. Therefore, with plants, it does not make sense to insist on rigid definitions, as plants are promiscuous in a certain way. They are constantly experimenting and testing their limits. What doesn’t work is forgotten and dies – what works can become a new plant species.

Plants are open systems

In the early 1980s, mutation breeding was supplemented by “green genetic engineering”. This makes it possible to specifically modify the properties of a plant by incorporating DNA from other genomes. In order to understand this new method of plant breeding, it is also necessary to understand other properties of plants: Plants are so-called “open systems”, which means that their stomata – through which they normally absorb CO2 and release O2 – provide a platform for microorganisms that can colonise the plant not only on the surface but also on the inside. As long as these co-inhabitants, such as viruses, bacteria or fungi, do not cause any problems, they are not noticed and are called “mutualists”. However, the proximity of plant cells and microorganisms can also lead to plant cells being able to take up the DNA of microorganisms from their immediate environment, and even use it, if it benefits them. This is where another special feature of plants comes into play: many plant cells have the property of “totipotency”, i.e. they can regenerate complete organs from certain parts. For example, if you put willow or hazel twigs in a vase, roots will form on the lower parts of the twig after a few days. And cutting tree stumps or shrubs can also regenerate sprouts.

This simple process has been used for centuries to propagate fruit and grape varieties. If one of the cells from which this regeneration takes place carries a mutation, this property is passed on to the offspring. Something similar happened to the sweet potato about 8,000 years ago: Four bacterial genes integrated into one genome and turned a wild plant into a crop. Today we know that a large number of plant species contain “bacterial genes” [2].

For plants, we need a new definition of what is and what is not a GMO

For this reason alone, the definition of a “genetically modified organism” (GMO) in the Genetic Engineering Act is no longer tenable based on current scientific knowledge. We need a new, scientifically based view of GMOs. In contrast, it makes little sense to evaluate the way in which a new plant variety has been created. For example, in the 1960s, long before one could even think of genetic engineering, a potato variety called “lenape” [3] was bred in the US. Not only could it be used to make crunchy chips, but it was also resistant to the main pests of cultivated potatoes based, unfortunately, on its high content of toxic plant substances. Fortunately, this was noticed in time. However, the same potato variety could still be conventionally bred today and widely marketed without there being mandatory safety checks.

Now we live in the time of “genome editing” by processes such as CRISPR/Cas and TALEN. Many argue that these methods of plant breeding would replace genetic engineering with its gene transfer. However, it must be countered by the fact that one can only edit genes that are present. In other words, classical genetic engineering thus remains part of the portfolio. All existing methods have their justification and can complement each other meaningfully. This is a prerequisite for solving the challenges of sustainable, intensified plant production under conditions of climate change and a growing world population. Let me remind you that we had our first commercial experience with classical genetic engineering almost 30 years ago. In contrast to induced mutations, we have extensive experience from safety research conducted worldwide that has not revealed any risks. So it is now high time to have a rethink!

[1] https://www.dropbox.com/s/g44tnh4i84toih7/MGG2017.pdf?dl=0

[2] https://pubmed.ncbi.nlm.nih.gov/31542868-widespread-occurrence-of-natural-genetic-transformation-of-plants-by-agrobacterium/

[3] http://www.gute-gene-schlechte-gene.de/gift-gene-zuchtung-lenape-kartoffel/