The secret of how cannabis got its high has been revealed by the world’s first cannabis chromosome map.
The breakthrough reveals the plant’s evolutionary past, and offers researchers new clues to how it and points to its future as potential medicine.
It found THC and CBD, the active substances produced by cannabis, appeared thanks to ancient colonization of the plant’s genome by viruses.
The team behind the study say it could lead to an explosion in Cannabis research.
‘The chromosome map is an important foundational resource for further research which, despite cannabis’ widespread use, has lagged behind other crops due to restrictive legislation,’ says Tim Hughes, a professor in the Donnelly Centre for Cellular and Biomolecular Research at the University of Toronto and co-leader of the study.
The virus find is only one of the insights revealed by the long-awaited cannabis genome map detailing gene arrangement on the chromosomes, published recently in the journal Genome Research.
Among other finds are discovery of a gene responsible for the production of cannabichromene, or CBC, a lesser known cannabinoid, as the active substances in cannabis are known, and new insights into how strain potency is determined.
How a Virus Changed Cannabis Forever
The enzymes making THC and CBD are encoded by THCA and CBDA synthase genes, respectively.
Both are found on chromosome 6 of the ten chromosomes the cannabis genome is packaged into.
There, the enzyme genes are surrounded by vast swathes of garbled DNA which came from viruses that colonized the genome millions of years ago.
This viral DNA, or retroelements as it is known, made copies of itself that spread across the genome by jumping into other sites in the host cell’s DNA.
New Cannabis Chromosome Map
The researchers expect the map will speed up breeding efforts to create new strains with desired medical properties as well as varieties that can be grown more sustainably, or with increased resistance to diseases and pests.
The new map reveals how hemp and marijuana, which belong to the same species Cannabis sativa, evolved as separate strains with distinct chemical properties.
Cannabis plants grown for drug use (‘marijuana’) are abundant in psychoactive tetrahydrocannabinol, or THC, whereas hemp produces cannabidiol, or CBD, popular in recent years for its medicinal potential.
Some people use CBD to relieve pain and it is also being tested as a treatment for epilepsy, schizophrenia and Alzheimer’s.
The enzymes making THC and CBD are encoded by THCA and CBDA synthase genes, respectively.
Both are found on chromosome 6 of the ten chromosomes the cannabis genome is packaged into.
There, the enzyme genes are surrounded by vast swathes of garbled DNA which came from viruses that colonized the genome millions of years ago.
This viral DNA, or retroelements as it is known, made copies of itself that spread across the genome by jumping into other sites in the host cell’s DNA.
‘Plant genomes can contain millions of retroelement copies,’ says van Bakel, an assistant professor in the Icahn Institute for Data Science and Genomic Technology in New York and in the department of Genetics and Genome Sciences.
‘This means that linking genes on chromosomes is analogous to assembling a huge puzzle where three quarters of the pieces are nearly the same color.
The researchers believe that gene duplication of the ancestral synthase gene and expanding retroelements drove ancient cannabis to split into chemically distinct types.
Humans then bred plants containing desirable chemistry such as high THC.
The gene sequences for the THCA and CBDA synthases are nearly identical, supporting the idea that they come from the same gene which was duplicated millions of years ago.
The chromosome map now clearly shows that two distinct genes are at play which should make it possible to separate them during breeding to grow plants without THC.
Some psychoactive effects in medical strains could be coming from CBC, a lesser known cannabinoid that has unusual pharmacology including anti-inflammatory properties.
The discovery of the gene responsible for CBC synthesis will make it possible for breeders to tailor its content in future varieties.
‘Mainstream science has still not done enough because of research restrictions,’ says Page, of UBC and Chief Scientific Officer at Aurora, one of Canada’s largest producers of medical cannabis.
‘Legalization and looming ease of research regulation really provide for opportunities for more research to be done. And Canada is leading the way.’
Did Early Christians Put Cannabis Extracts in Their Anointing Oils?
Some cannabis advocates claim early Christians, including Jesus himself, put cannabis in annointing oils used to heal the sick and elderly.
The Hebrew version of the holy oil recipe in Exodus includes kaneh-bosem, a mysterious herb that some suggest was a cannabis extract.
This extract, which was absorbed into the skin, could have helped cure people with physical and mental illnesses long before the first mass-produced medicines.
Historians and other experts strongly dispute the claims Jesus and his apostles used marijuana.
Lytton John Musselman, a Professor of Botany at Old Dominion University, said evidence claiming marijuana was part of the holy anointing oil is ‘so weak I would not pursue it.’
He told Vice that keneh-bosum more likely refers to calamus than any psychoactive substances.
‘Calamus is a very important component of Ayurvedic medicine and has been shown to have efficacy,’ he said.
‘For example, in Sri Lanka it is available in any herbal remedy shop and also universally grown in home gardens.
‘The North American species was and is so important to Native Americans in the Northeast that land with natural populations is highly sought after.’
Source: DailyMail