How Can You Genetically Engineer a Plant?
By Izabela Ninu
Is there any simpler method to use than CRISPR-Cas9?
We have talked in previous articles about plasmids, about CRISPR, about genetically engineered plants… is there any simpler way? Indeed, this is another naturally occurring bacteria that has helped shape the way we use GMOs and how we address them. Just like the streptococcus bacteria in milk cultures, this is a bacteria that infects the plants.
What does it cause?
Just as the name — Agrobacterium tumefaciens — implies, this bacteria will cause a tumor in the plant.
We have all seen this kind of weird-looking grown-parts of the tree: these are called tumors, indeed. The principle of operation is simple: the bacteria will infect the plant, and will transport its bacterial DNA causing the tumor into the DNA of the plant, which will, in result, develop this phenomenon.
Usually, this happens in a tree. However, many researches have shown that the agrobacterium transported genes can also be found in plants such as sweet potatoes or tobacco. These are, as such, naturally induced “Genetically Modified Organisms”, that we may eat without even knowing!
This is, simplified, how the agrobacterium operates: the receptors at the membrane of the cell will create a tunnel through which a plasmid fragment, the T-DNA, will be cut and integrated into the nucleus of the host plant cell, creating the virulence. It is a system that is auto-mediated, creating a continuous cycle, the most impressive part of the system of this bacteria.
First of all, the virulence region of the plasmid — vir — encodes for some proteins, such as VirD2 and VirE2 that will facilitate the injection of the T-DNA into the plant cell.
Furthermore, the opine catabolism region is a really interesting part of the cell: the opine is the nutrient that is used by the cell in order to function, and this gene is going to encode for the catabolism of that opine (so the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reaction, basically the breaking down of the molecule).
Then, we are looking into the T-DNA region, contained between its two borders. We will find there the Opine gene: the creation of the “food” for the bacteria to self-sustain, making it a really useful process. It will also contain the Cytokinin and Auxin gene regions: the two will encode for two growth factors. As such, once the T-DNA region will be inserted into the plant, it will be able to produce the growth for the virulence and the nutrients for the growth.
As you can imagine, this system of the agrobacterium will be massively used with the insertion of other genes into the TI plasmid that we are interested in, in order to insert it into a plant that will therefore express the specific gene; this is going to be another genetic modification technique. (it will be used together with floral dipping, but that is a matter for another time).
