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Unlocking the Molecular Puzzle of Cannabis

Rumours of genetically modified cannabis lack evidence, especially since decoding the cannabis genome is just a budding field

Take-home message:
- There is no evidence for the existence of GMO weed.
- Genetic information shows that labels in cannabis shops (about strain, ancestry, and name) cannot be trusted.

Despite what some chronic users may claim, the cannabis plant is not mystical. Like any living species, its cells house genes that encode proteins which, through an impressively choreographed dance influenced by the environment, yield a distinct organism.

The very molecules responsible for marijuana’s effects are encoded in these genes. If this genetic code could be modified, human beings could precisely control the levels of these substances in much the same way that a sound engineer can alter music with a mixing console. With genetic engineering, the levels of THC, the chemical responsible for marijuana’s “high,” or that of cannabidiol, responsible for its medicinal properties could be boosted.

Of course, some people will tell you that this has already happened. There’s a rumour, probably still alive in many Facebook groups, that Monsanto has created “GMO weed,” terrorizing people who fear that they may inadvertanly be exposed to those dreaded GMOs. When the debunking website investigated the claim, they found it had originated on a “fake news” website. Satirical hoaxes meant “for entertainment purposes only” have an unfortunate way of becoming “truthiness” in the telephone game of social media.

The Huffington Post itself contributed to this rumour mill in 2012 when it reported that a scientific study had possibly detected the presence of genetically modified cannabis in police seizures. How could they even tell that the illicit substance had been modified at the genetic level, you may ask? The gene that gets inserted in the lab is often accompanied by a “marker” gene, the expression of which can be clearly detected. For example, the marker gene may generate a fluorescent green colour. If you see the colour, you know that both the marker and the gene of interest have been inserted into the genome. So scientists can look for traces of common marker genes in the cannabis genome as an indication that they may have GMO weed on their hands.

But did they find any? The study cited byHuffPohad scientists testing 38 samples of cannabis and hashish obtained by law enforcement. They could not detect any trace of marker genes in any of the tested samples… except for one. However, street samples are notoriously impure. As the scientists themselves pointed out, it is much more likely that the marker came from a genetically engineered “cover crop” used to mask the illegal growing of cannabis. So far, there is no evidence for the existence of genetically engineered cannabis.

The cannabis puzzle

What these unfounded rumours about “super weed” obscure is the fact that, actually, we really don’t know much about the genetic code at the core of the cannabis plant. This might be surprising in the era of the Human Genome Project and the promises of personalized medicine, but the genetic cogs and wheels of marijuana remain somewhat concealed.

The main reason is obvious: cannabis is an illegal crop and researching it requires the kind of paperwork that would make a committed bureaucrat blush with envy. But it’s not the only reason.

Sequencing an entire genome—meaning reading the genetic code letter by letter—can’t be done in one go (unlike reading a really good book cover to cover). Rather, it’s accomplished with overlapping fragments. Imagine if a hundred copies of this article were cut up in random scraps of 15 consecutive letters. You could put the article back together because of the overlap between the scraps. But if I added the sentence “This is a repeat, I repeat, this is a repeat” throughout my article, the puzzle would become a bit of a nightmare. This is the challenge faced by plant geneticists studying cannabis. The plant naturally has many, many repeats in its genome. It also has duplicates of important genes, a sort of genetic backup. And humans haven’t helped either: there’s been so much crossbreeding of marijuana (mainly to increase its buzz) that contemporary plants often contain many copies of the genes coding for the psychoactive THC molecule. Imagine being given a book filled to the brim with repeated sentences, put through a shredder, and asked to put it back together. If this sort of challenge electrifies you, the field of plant genetics awaits your contributions.

We do have some genetic information about cannabis, however, little snapshots of its genome, as well as the complete sequence of the Purple Kush strain. And this information is challenging received wisdom.

From likely to hazy

One of the most basic facts about pot is that there are two main varieties. Sativa plants contain a stimulating type of marijuana. These plants grow tall and narrow. Indica strains, by comparison, sedate your body and come from plants both short and wide.

Sativa stimulates. Indica relaxes.

Except these once distinct lines have become increasingly blurred because of crossbreeding. What looks like a sativa plant may actually be an indica plant and vice versa. A group from Canada pointed this out ina 2015 article. They tested Jamaican Lambs Bread cannabis, which was sold as a sativa strain, only to find out that it was genetically identical to an indica strain from Afghanistan. Sample mix-up could have occurred, but the rest of their experiment demonstrates that, at the very least, the indica/sativa distinction is becoming hazy.

But surely Jamaican Lambs Bread is the same wherever you buy it… right? Actually, no. The same genetic study revealed that, in a set of 17 samples, 6 were actually more similar to marijuana samples bearing a completely different name than to other samples of the same variety. If the same thing was found for breakfast cereals, it’s safe to say there would be an uproar.

Learning more about the genetics of the cannabis plant will require an easier legal framework as well as better technology. But already, what little we know about the inner workings of cannabis is changing much of our received wisdom.

For those who want to delve deeper into “Getting other organisms to produce cannabinoids“, click here

There is another way to use molecular biology to play with cannabis aside from genetic engineering. The goal is to get a living organism other than the cannabis plant… to produce cannabinoids. This project came about because the cannabis plant produces a number of interesting compounds called cannabinoids which can interact with receptors in our brain. Some, like THC and CBD, are present in large quantities, but many are only made by the plant in tiny amounts. Because of that, they are difficult to extract in large quantities, and synthesizing them in a laboratory using chemical reactions has so far failed to be cost-effective. Thus the idea becomes to use what is called synthetic biology: transforming E. coli bacteria, yeast cells, and plants other than cannabis to produce these compounds. The challenges? This transformation has so far been very inefficient and the host organism has to be protected from the very cannabinoids we want it to produce, the reason being that cannabinoids are actually a defence system for the cannabis plant. 


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