- Engineered food
The characteristics of plants depends, for a significant part, on the DNA of that species (clearly the way the plant grew, the terrain, the amount of water…are additional factors). These characteristics include the ones we experience when we eat that plant (and the ways it can be prepared and cooked) but they also affect its growth, its resistance to adverse conditions (including sensitivity to pests and diseases) and its conservation once harvested.
A lot of the economics is dependent on these characteristics: a plant more sensitive to pests requires more pesticides and its cost increases, a plant that grows faster leads to increased yield, hence generate more revenues, a plant that resists better to transportation can be marketed in far away places increasing its potential market, a plant that has a more pleasing colour or shape can be get a higher price on the market, a plant that can grow in an infertile soil can produce revenues where it was not possible before, … The list is quite long.
By cross breeding and other agricultural techniques that have been developed over millennia farmers have been able to increase their revenues.
As shown in the chart, today’s technology is offering the possibility of tailoring the characteristics of plants “forcing” changes in their DNA. In particular we can see five approaches:
- Protoplast fusion
- Genome Editing
This is a process that occurs in Nature. A cell is exposed to some mutagen factor (radioactivity or certain chemicals) with the result of changing its DNA. If this is a cell involved in the reproduction of that plant (or animal, all theses changes being considered applied to both animals and plants, although here we are considering them in relation to agriculture) then the modification affects its offsprings. This is a random modification. Most of the times the offsprings are sterile and the modification does not generate a new variety. In those cases that the offspring are fertile the variation may be advantageous to the plant and will tend to propagate. Of these cases we are interested in the variations leading to an advantage from the farmer point of view. This is clearly a sub-subset of all possible mutations. Actually the probability of a random change to result in a “better” plant is extremely low, and that explains the very slow evolution we have seen over the millennia.
By intentionally using mutagens, like exposing the plant to radiation, we can increase the rate of change and increase the chance of getting a “better” plant. However, the random processes leading to a variation are far from optimal in terms of effectiveness of result. More recently researchers have been able to use specific mutagens to steer the evolution in specific directions (like creating a plant that requires less watering). In these cases the efficiency can increase. The whole mutagenesis process occurs through a repetitive cycle (see the graphic) that increases its effectiveness.
Protoplast fusion allows the transfer of some desirable characteristics, like resistance to diseases, from one plant to another. The challenge is to create an hybrid that is fertile. This has proven difficult when the fusion occurs between plants that are quite different from one another so researchers have been focussing on plants that are genetically similar.
Since the turn of the century significant progress has been made with this technology. Using this technology has been possible to insert bacteria fixing nitrogen in plants that were without them and to increase the effectiveness in photosyntheses by using better chloroplasts, thus increasing the growth rate.
We have two sets of chromosomes, one inherited from our father and one from our mother. This is what scientists call “diploid”. In plants it is not uncommon to have multiple sets of chromosomes, derived from the parents -multiple parents. This expands the characteristics of a plant, creating variety (since sometime one chromosome is at work, some other time another in the same set). This is a natural occurrence in Nature , wheat as an example is hexaploid, having -in a way- 6 chromosomes duplication – like having 6 parents- and what researchers have been doing is finding technologies that allow them to create polyploid plants, thus accelerating diversity creation.
Very recently, on May 11th 2018, the Chinese Academy of Science announced the artificial generation of high quality wheat by fostering polyploidy of specific type in wheat (wheat has a longer genome than human beings, 5G vs our 3G, a good 60% more).
In the last 20 years researchers have been able to change the genome by cutting and paste in codons. The technology used is CRISPR/Cas 9 and has been “borrowed” from bacteria that use this approach to fight invading viruses.
By applying CRISPR/Cas 9 it becomes possible to engineer the desired characteristics of a plant, by manipulating the instructions that create the plant. It is no longer pursuing random changes in the genome (mutations) nor adding characteristics borrowed from other plants (protoplasm fusion) nor adding instructions taken from another plant at chromosomal level (polyploidy). Here we are changing the native set of instructions contained in the plant DNA. In a way this is a most effective way, at the same time it creates greater ethical issues than the other approaches.
In transgenesis a gene taken from a cell of one species (plant an animal alike) is inserted in the cell of another species creating a transgenic organisms. This is something that would seldom occur in Nature (in theory a virus can steal a gene from a cell it has infected and carried it over to another plant that it will infect dropping the gene that from that moment on will become part of the newly infected cell. In practice the probability of a virus infecting a spermatic cell or an oocyte immediately before fertilisation so that it will become part of the creation of a mutant is extremely low).
Monsanto has been using transgenic technology, as an example, to create papayas resistant to the papaya ringspot virus.
Nature has been carried out species modification since the beginning of life, and that is the reason why we are here today. Without random mutations, and selection, we would not have the diversity of life we see today on the planet (which is but a small subset of the diversity of life in the history of Earth, with most species having disappeared long time ago…). Hence, what scientists are doing is simply to accelerate the process and direct it to achieve desirable results.
In the 4 billion years of evolution Nature made plenty of mistakes, actually just an infinitesimal fraction of all mutations proved viable and “good” from an evolutionary point of view. The big issue confronting scientists, and raising concern in the public opinion, is that we don’t know if an induced mutation si good or not (and it is debatable what it is meant by good!) and that is something that might take years, centuries to discover. Are we pressing our luck in tweaking with the code of life?
Interestingly, artificial intelligence and deep learning technologies are now being explored to help understanding the implication of changing a genome, and a species. We do not have a clear understanding of what happens to the phenotype (the characteristic of a living being) when we change its genotype (change the code of life). This is now being addressed through artificial intelligence tools.