Cannabis derives its highly inductive power from ancient viruses


We humans love cannabis for a variety of reasons, but they usually boil down to one of two things: THC (tetrahydrocannabinol), the psychoactive component that propels you like a bird; and CBD (cannabidiol), primarily sought for its medicinal effects in the treatment of diseases such as epilepsy and potentially other health benefits. In the end, you can thank viruses, millions of years ago, for giving cannabis the ability to produce these two chemicals.

In the latest issue of Genome Research, a group of North American scientists published for the first time a complete map of the cannabis genome. Among the countless interesting information to draw from the table, there is the discovery that the genes coding for the production of THC and CBD have evolved through DNA fragments introduced by viruses that have infected the plant and the disease. They colonized successfully millions of years ago.

The discovery of the gene responsible for the production of CBC (cannabichromene – one of the cannabinoids present in marijuana), the differentiation of hemp and marijuana (the first product mainly of CBD, the second being full of THC), and clues about what could make another cannabis more powerful and more robust than others.

"One of the problems associated with the reproduction of cannabis has been the resources associated with the genome examination," says Todd Michael, director of computer science at the J. Craig Venter Institute in La Jolla, in California, who did not participate in the study. Until now, much of the work has involved some sort of random selection process of random strains, without much knowledge about the transferred genetic traits. "A resource such as a genetic map is really the starting point for a high quality selection, for any plant," says Michael. "All the really important crops need it."

But in the past, the development of such a map for cannabis has been hampered by obstacles. Legislation has prevented researchers from easily studying and experimenting with plants, even in controlled laboratories. In addition, it is inherently difficult to map the genome of cannabis because of its relatively large size. The larger the genome, the more difficult it is to categorize it. This is why scientists have so long to map and make sense of the human genome. The difficulty in sequencing and assembling the cannabis genome has been compounded by the viral elements. You see, THC and CBD are made by synthase genes that are on the same chromosome. But these synthase genes are invaded by truncated DNA fragments called retrotransposons, which come from viruses, you guessed it. Over time, these millions of infectious DNA elements have multiplied and spread throughout the genome. The THC and CBD synthase genes are firmly embedded in these elements.

It appears that the THC and CBD synthase genes originate from a single gene, and that the viral retrotransposons, when they jumped and extended, caused the gene sequences of the synthase to mutate in different strains of cannabis, which stimulated divergence of the gene into THCA (producing THC). ) in marijuana and CBDA (producing CBD) in hemp. Michael suggests that transposable elements might have been able to carry and displace the synthase gene around him as they jumped into the genome.

The original team had previously published a genome project in 2011, although it was too fragmented to indicate where specific genes on chromosomes were located. Another genetics company revealed a cannabis genome map in February, but has not yet released the results.

According to Michael, the complete mapping of the genome will be "revolutionary" for the cannabis industry. Industry experts will be much easier to identify the characteristics to select in order to produce easier and faster strains to develop. But in addition to turning cannabis into a higher growing crop, the genome map should also have a significant impact on adjusting the ability of a strain to produce THC, CBD and hundreds of other cannabinoids. specific to cannabis.

"Combining a genetic map with a high quality genome could eventually allow scientists to target specific pathways, especially for people interested in the psychoactive components of cannabis," says Michael. For example, you can modify the terpenic profile of cannabis to modulate the high level of the plant. You can also change the type of odors produced by the plant. Armed with the genome map, researchers could even use a tool such as CRISPR to directly modify these characteristics at the genetic level.

Although the role of the old viral elements in the evolutionary history of THC and CBD production is an interesting idea, for most scientists this is not so surprising. "In general, that's how plants evolve," says Michael. "I'm not really sure why the media has taken it so aggressively." Researchers have known for a long time that retrotransposons have viral origins. "We know that the genome size in plants is almost 100% due to the expansion of retrotransposons.This is not new.And we know that they play a big role in the 39, evolution of plants. "

Instead, Michael argues that the most critical information in the paper is to illustrate which genes may or may not be active, as this will allow researchers to better understand what points need to be reworked and what areas need to be avoided.

Michael is particularly excited about the future of high-content CBD products as a substitute for opioids. "We have a huge epidemic of opioids," he said, "and it has been shown that CBD and THC can play a role in pain management."

In the end, the new genome map will spawn many new works in the recreational and medicinal applications of cannabis. "There is a lot of great work going on," says Michael. "Over the next year, we will see a lot of really fantastic things in genomics of cannabis."