Cannabis Unravelled

For over a millennium marijuana has been used for both its medicinal and recreational properties. Yet the origins of the ingredient that makes is psychoactive- tetrahydrocannabinolic acid (THCA) – was unknown, until now.
The unique pharmacological properties of cannabis are due to the presence of cannabinoids, a group of more than 100 natural products that mainly accumulate in female flowers buds. Why certain types of cannabinoids are only found in marijuana was unclear.
A team of researchers, led by Jonathan Page and Timothy Hughes from Canada wanted to solve the mystery of a plant whose genome had not yet been published. In order to figure out why cannabis plants are known for their Dr Jekyll style “split personality”, as claimed by Noami Attar in Transcriptome Biology. How come marijuana gets you high, but hemp does not?
Genome sequencing has revealed that marijuana (Cannabis sativa L.) does contain the potent psychoactive chemical THCA, but hemp (Cannabis L.) doesn’t. The researchers sequenced the genome of a marijuana strain called ‘Purple Kush’ and compared it to ‘Finola’ hemp. The hemp only contained a non-psychoactive cannabinoid, cannabidiolic acid (CBDA).
The research was published in BioMed Central’s open access journal Genome Biology and Dr Page explained that “a detailed analysis of the two genomes suggests that domestication, cultivation, and breeding of marijuana strains has caused the loss of the enzyme CBDA synthase.” Further analysis showed that a gene responsible for THCA production was “switched on” in marijuana but had been “turned off” in hemp.
The researchers used RNA-sequencing to analyse the enzyme transcriptome. It revealed strikingly different gene expression levels in the hemp and marijuana strains. The genes responsible for a particular coding protein (THCA synthase enzyme) were more abundant in marijuana, meaning higher levels of THCA production.
Today, common derivatives of cannabis such as hashish are the most widely consumed illicit drugs in the world. Their use has also been recognised in the treatment of multiple sclerosis and chronic pain. Hemp seeds are also a very good source of fibre, oil and proteins.
Dr Page adds: “Decoding the cannabis genome will help answer basic questions about the biology of Cannabis sativa and further the development of its myriad applications including strains for pharmaceutical production, and the breeding of hemp plants with improved agronomic characteristics and fatty acid profiles.”