While the genome of the cannabis plant was sequenced in 2011, the researchers struggled to isolate the genes responsible for producing the two most important chemicals in the plant.
Until now. A joint Canada-US effort has helpedidentifier the genes that produce THC (the component that causes hovering) and CBD (the compound best known for its medical applications).
The main obstacle to discovering these genes was the abundance of what researchers call "junk DNA," a genetic information that was dumped into the genome of cannabis by viruses during the years of its evolution. In fact, between 70 and 75 percent of marijuana and hemp DNA comes from these retroviral sources, says Tim Hughes, a molecular geneticist at the Donnelly Center for Cellular and Biomolecular Research at the University of Toronto.
For example retroviruses: like HIV, are able to insert their DNA into the genomes of other species, says Hughes.
"Humans, plants, and virtually all organisms have something like that - about half of the human genome goes back to viral sources.
According to researchersThis discovery will greatly facilitate the manipulation of medicinal THC and CBD levels contained in the plant to meet the varied preferences of patients in the newly legalized Canadian market.
"You can only handle a gene when you know where it is"
said Harm van Bakel, one of the collaborators of the study, who is also an expert in genomics at the Icahn School of Medicine in Mount Sinai, New York.
"And you also need to know about the rest of the genome sequencing so you can uniquely target the gene of interest and not be distracted by ... other things that look like it," Bakel said. The Toronto Star.
But not only did this mass of viral DNA prevent researchers from seeing the THC and CBD genes, but it probably also contributed to their development. Hughes says that the cellular mechanisms that would normally maintain the genetic order may be thwarted by the long and repeated sequences of the surrounding viral DNA. And instead of keeping the genes in their original form, the faulty mechanisms would have reorganized their sequencing to produce the current genetic patterns. Exposing cellular mechanisms to viral DNA can cause errors that lead to genetic changes in plants such as cannabis.
According to Tim Hughes, these "mistakes" have "almost certainly" favored the development of the THC and CBD genes of the plant.
The study, of which a preliminary version was published online this month by the journal Genome Research, has also shown that THC and CBD are produced by distinct genes.
The existence of another active gene that produces a product known as cannabichromone, or CBCcan have both medicinal and slightly intoxicating effects in humans.
Another reason that genes had escaped scientists was the illegal status of the plant. Ironically, although we understand quite well how THC and CBD affect humans, we do not know how the genes that produce them are for the plant itself.
The discovery of the genes will make it much easier to grow cannabis with specific levels of the two primary compounds. It also allows researchers to determine which genes are responsible taste and smell which characterize the different strains. Yet, even though the genome with 10 chromosomes has been sequenced in 2011, the location of these key genes has remained hidden in an ocean of viral DNA until today ...