Jellyfish eggs with Crispr
The benefits of Crispr technology for agriculture is infinite – from virus-resistant banana cultivars and caffeine-free coffee to drought-resistant maize, and even gluten-free wheat. However, the large-scale adoption of the technology is hampered by regulatory hurdles and ethical considerations.
The path of scientific discovery often follows a pattern of slow progress that can build up to a sudden breakthrough. Crispr is one such breakthrough that can be revolutionary, both for the medical and agricultural industry. In 2020, two women, profs Emmanuelle Charpentier and Jennifer Doudna, jointly received the Nobel Prize for Chemistry for developing this genetic editing method.
Although genetic modification has been around for several years, it has been a very blunt technology until now. Crispr is both cheaper and more accurate – it is like the difference between a computerised laser cutter and a hacksaw. For example, the creation of glyphosate- (Roundup-) tolerant maize involved genes for glyphosate tolerance being shot into a bundle of maize cells with an air ‘rifle’ with the hope that some of them would be incorporated. The maize cells in turn are multiplied and then treated with glyphosate, with the hope that some would have incorporated the resistance genes.
With Crispr technology, the specific gene for glyphosate resistance can be incorporated into the maize DNA with precision. Not only can the intended pieces of DNA be transferred between organisms, but Crispr can also be used to cut out, or deactivate parts of an organism’s own DNA.
Exact Genetic Modification
Charpentier and Doudna did not set out to develop Crispr, in fact they were simply interested in understanding how bacteria defend themselves against viruses. A virus is a very simple organism which consist of a string of genetic material (DNA) surrounded by a capsule with a deposit mechanism. When a virus attacks a cell, the virus simply deposits its DNA inside the victim cell. The virus DNA then hijacks the host cell’s cell division mechanism to make copies of itself until the attacked cell bursts and/or dies.
To protect themselves against virus infections, the bacteria incorporate parts of the virus DNA into their own DNA. In doing so, they have a genetic memory with which they, and their offspring, can identify and eliminate the DNA of attacking viruses.
The mechanism with which they cut their own DNA and insert the virus DNA, is accomplished by so-called Crispr proteins. Charpentier and Doudna developed a way in which geneticists can use a modified version of this mechanism for exact genetic modification.
This technology has very exciting applications for human health, like the treatment of cancer and genetic diseases in adults. Theoretically, it can cure communicable genetic diseases if it is applied to embryos, because the whole genome would then be modified. A good candidate for this is the curing of cystic fibrosis and sickle-cell anaemia. At this stage, the application of this technology in humans is subject to several ethical and regulatory hurdles.
Beneficial for agriculture
Apart from the human applications, there are also exciting opportunities in agriculture. One such application of Crispr is with laying hens. Approximately 14 billion eggs are hatched globally each year for the provision replacement of laying hens, unfortunately the sex of the eggs can only be determined after they are hatched. The result is that half of them – approximately seven billion male chicks – must be disposed of each year.
However, EggsXyt, an Israeli company, managed to use Crispr to transfer the DNA of a jellyfish into the male chromosome of the laying chickens. The effect is that when a bright light is shone through the genetically modified eggs, the female eggs will show nothing, but the male eggs will appear blue. They can then be removed before hatching, this saves substantial costs and many chickens’ lives. There is also no risk to the consumer, since only the male chromosome was altered in the process. Thus, the genetic composition of the laying hens and their eggs are intact.
This technology is ready for commercial use but must still overcome various regulatory hurdles. However, it seems as though the regulatory restraints are not unsurmountable. Various designer food products with Crispr-modified DNA have already been approved for use in America. Examples are mushrooms that do not go brown after harvesting, flax seeds with a high omega-3 fatty-acid content typically found in fish, and waxy maize with high amylopectin levels which gives them properties like those of cassava (from which sago is made). Other examples of agricultural applications are banana cultivars that are immune to virus diseases, grapes that are resistant to downy mildew, coffee that is naturally caffeine-free, gluten-free wheat and drought-resistant maize.
The application of Crispr in agriculture is currently expanding. If the regulatory and ethical restrictions can be overcome, the biggest limitation would simply be a person’s imagination (and money). The current applications are only the tip of the iceberg!