Oh no, GM-crops! The horror! The pain! The unhealthy side effects!
Over the years, GMOs (genetically modified organisms) have caused concern in many people. But what is a genetically modified organism? Is it really that dangerous? And if not, why are people so worried?
There are actually two definitions of transgenic:
- Organisms containing an artificially introduced change in their genome
- Stable introduction of a foreign gene into an organism
But what does that mean?
Artificially Introduced Change
What happens if you shoot something with radiation? The DNA changes. In humans, that often leads to cancer and/or death. But plants are cool, plants can deal with that. They’re a lot better at healing and generally regenerating themselves than we are.
People have been using this fact since the 1930’s … and are still today! Plants are irradiated with γ-radiation or treated with mutagenic chemicals. And then they mutate. Scientists look at those plants and take those that have now developed properties they want, be it bigger fruits, better taste or whatever.
The changes in the DNA happen randomly and can’t be predicted.
Foreign Genes
The word foreign is actually a bit misleading. Yes, the DNA that’s introduced can come from a different organism but it can also come from the same or a similar organism! That would be called cisgenic instead of transgenic. It falls under the same set of rules.
There are several ways of introducing genes into a plant. Through microinjections, with chemicals, with a so-called “gene gun” or by using other organisms that do the work. Yesterday I already introduced you to Agrobacterium tumefaciens, which is used to induce mutations in Arabidopsis thaliana. This is a typical example of the insertion of foreign genes.
But wait, there are naturally occurring organisms that cause transgenic plants?
Nature, the greatest Genetic Engineer
A. tumefaciens can be found basically everywhere in the soil. It can sense when a plant is wounded (because plants send out certain chemicals when that happens) and then move towards the wound. They enter the plant and then insert some of their own genes into the plant’s genome.
When activated, the new genes cause the plant’s cells to divide over and over again and produce growth hormones, causing a tumor. This is also called crown gall disease. The tumor provides perfect living conditions for the bacterium and the plant can usually still survive. As I said before, plants are incredibly resistant.
Parts of the bacteria genome can also be integrated into random parts of the plant’s genome which causes disruptions and mutations.
That’s useful for the lab, as we can just remove the “tumor” parts and keep the “causes random mutations” parts.
You might (or might not) ask yourself “Okay, there is a natural way to create transgenic plants, but what about cisgenic plants?”. Fear not! I can answer that too! With one of my favorite concepts: The jumping genes.
Jumping genes have first been discovered in Zea mays (corn). Did you know that this plant wasn’t originally yellow? Nowadays you can find it in many different color variations, often several colors on just one cob!
That’s the work of jumping genes, also called transposons.
There are two kinds of jumping genes, those who can jump without help (they usually produce the enzymes they need to jump themselves) and those who can not jump by themselves (but with the help of other genes that cause the production of the necessary enzymes).
Puh, that might be a bit heavy, especially because there are several categories of all this. But I will make it short and explain it with an autonomous transposon (a gene that can jump by itself).
The gene is somewhere in the DNA. For some reason, it is activated, and the cell starts producing an enzyme. This enzyme either copies the gene or cuts it out. The cutout gene (or the copy) can now be randomly inserted into another part of the DNA and can possibly interrupt a gene. They can also land somewhere totally harmless.
So, it’s either Copy & Paste or Cut & Paste.
In Zea mays the copy/cut & paste causes a change in color. In a way, this is the creation of a natural cisgenic organism.
Is it Bad?!
It’s hard to answer this question with a definite “yes” or “no” because of the many aspects in play. In itself, a GMO isn’t necessarily dangerous. In most countries, GM-crops need to be thoroughly tested before they are allowed for human consumption.
But.
The creation of herbicide resistant GM-crops lead to a very … liberate use of herbicides, because it doesn’t harm the crops anymore.
But.
Non-GM-crops are also sprayed with herbicides and the quantities aren’t harmless either. So it’s not really about GM vs. non-GM but more about people just feeling the need to spray herbicides and pesticides and whatnot on everything.
But.
Herbicides and Pesticides are somewhat necessary for large-scale farming. It’s not easy and we should all keep working on a solution. But for that, people have to understand what GMOs actually are and that they’re not necessarily the problem.
And they’re by far not as artificial as one tends to believe.
Sources:
Agrobacterium tumefaciens: a natural tool for plant transformation
Barbara McClintock and the Discovery of Jumping Genes (Transposons)
Transposons: The Jumping Genes
Lecture “Transgenic Plants - Facts and Fiction” by Katrin Philippar
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