Imagine being able to take a small, bitter, wild eggplant and with a single genetic tweak, turn it into a very different variety, much larger and ready for the market. This, it seems something out of a science fiction movieit may be a reality that is getting closer, as one pointed out published study in the magazine Nature who deciphered the genetic “instruction manual” of the entire eggplant family and also the tomato.
The problem. We are currently living in a time in which the climate is changing radically. with increases in temperatures or reduction in rainfall that reach our fields. This forces us to have a ‘plan B’ in the bedroom that allows us to continue having crops efficiently and to be able to feed an entire population despite there being a climate decline. And genetics in this case is preparing for it with different changes.
The agriculture of the genetically modified foods is starting to gain strength. The fact of modifying the seed of a fruit so that it comes out with significant improvements, such as being juicier, larger or more efficient, is the future of agri-food engineering. And all to be able to respond to an increasingly growing demand for food, but with a space suitable for it that is smaller.
A commitment to flavor. But these genetic alterations raise many questions. The goal right now is to have fat tomatoes or eggplants that are also very elongated but without thinking about anything else. If we eat a tomato on many occasions what we want is for it to be juicy and good. But genetic modification may overlooks these types of essential components to be more ‘productive’ and nutritious.
But the objective in this case of the investigation that is currently being carried out is on size. And if one tomato ‘from the future’ can be equivalent to three ‘current’ ones, the truth is that we will have taken a very important step. And this is already being seen.
The investigation. An international team of scientists has created the first “pangenome“of the genus Solanum. This is not only the tomato and eggplant family, but also the potato and dozens of other crops consumed locally around the world, and which opens the door to a great evolution in the field of food and the agri-food industry.
The objective. For the researchers, the objective was quite clear from the first moment: to know why a gene that produces a desirable trait, such as having a larger fruit in a tomato, does not work when tried to apply it to an eggplant. The answer in this case is quite clear: genetic redundancy.
The obstacle. In this case, scientists saw that the main obstacle to this genetic modification not being applied was in gene duplications, known as paralogues. In order to understand this concept we can imagine the light in a room that would be our phenotype and that in order to turn it off we need to press two switches that control it.
These switches are what we know as paralogs, and in order to turn off the light it would be necessary to deactivate both. This is what happens in many species, which have created ‘backup copies’ of their switches so that turning off just one would do absolutely nothing and would not materialize in their phenotype, such as their size.
That is why this team analyzed 22 species of Solanum and discovered that, although the overall structure of chromosomes is similar, thousands of key genes have undergone different variations throughout their evolution.
The brake gene. Scientists have long known that a gene called CLAVATA3 (CLV3) is the master regulator of fruit size in tomatoes. Its function is, basically, to act as a brake. It tells stem cells at the plant’s growing points (the meristems) when to stop dividing.
Thus, when this gene is mutated or ‘off’ the brake is released and the plate produces more cells, resulting in larger flowers with more seed compartments and also a much larger fruit. And here is the key to how a tomato will end up being domesticated.
The problem is that the tomato has an additional “handbrake”, which is a paralogous gene called CLE9. In this way, even if we alter CLV3, it will not have its full effect, since it will have this extra switch that must also be altered.
CRISPR. It is a genetic ‘editing weapon’ that will allow us to achieve the effect we want and cut the brake on CLV3 so that the fruits can evolve. The scientists ran the tests on the African eggplant, a species that lost its CLE9 handbrake a long time ago, but has a functional copy of CLV3. When scientists used CRISPR to deactivate that only functional copy, the result was massive and uncontrolled growth, demonstrating that that gene was the only brake he had left.
In another experiment, we used S.prinophyllum that did not have CLE9, but did have two units of CLV3 (CLV3a and CLV3b). In this case, when the researchers edited a single copy, the brake was weakened and the plant produced fruits with more lobes and therefore slightly larger fruits. But when they removed the two brakes, uncontrolled growth was seen again.
The surprise find. While research was being carried out along these lines, experts saw something they did not expect: a completely different gene on chromosome 2 called SaetSCPL25-like acted as the main size “switch” in the African eggplant. Something that responded to a small natural mutation of this gene that was associated with the additional locules per fruit.
To check this, they did the experiment in reverse. They took this new gene and they cracked it with CRISPR on a standard tomato. The result in this case is that fruits were produced with more locules, that is, they were much larger. In this way, the researchers had found a second genetic path to increase the size of the fruit in addition to breaking its brakes.
An agricultural revolution. This study not only gives us the secret to creating very large tomatoes and eggplants. It’s a detailed map that tells us what genetic “backups” each plant has. Before, genetic engineering in crops was a very risky bet. Now scientists can consult this pangenome, see if the eggplant they want to improve has one, two or three “switches” for the trait they want to exploit, and design an editing strategy in the laboratory.
In this way, you can improve the size of the fruits to be more efficient, but you can also try to edit the flowering time or drought resistance. In the end, what is allowed is to quickly adapt local crops to new climates.
Although in this case different doubts may arise in the field of ethics, since there are many people who categorically reject the consumption of foods that have been genetically edited in a laboratory to be much more efficient.
Images | Anna Evans
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