重口味SM

Cannabis sativa produces both industrial hemp and marijuana.

How hemp got high

Genetic changes led to marijuana's drug-producing properties

A team of Canadian researchers has sequenced the genome of Cannabis sativa, the plant that produces both industrial hemp and marijuana, and in the process revealed the genetic changes that led to the plant鈥檚 drug-producing properties.

Jon Page is a plant biochemist and adjunct professor of biology at the University of Saskatchewan. He explains that a simple genetic switch is likely responsible for the production of THCA, or tetrahydrocannabinolic acid, the precursor of the active ingredient in marijuana.

鈥淭he transcriptome analysis showed that the THCA synthase gene, an essential enzyme in THCA production, is turned on in marijuana, but switched off in hemp,鈥 Page said.

Tim Hughes, co-leader of the project, is a professor at the Terrence Donnelly Centre for Cellular and Biomolecular Research and the Department of Molecular Genetics at the 重口味SM. He explains the team compared the potent Purple Kush marijuana variety with 鈥楩inola鈥 hemp, which is grown for seed production. Hemp lacks THCA, but does contain another, non-psychoactive substance called CBDA, or cannabidiolic acid.

鈥淒etailed analysis of the two genomes suggests that domestication, cultivation, and breeding of marijuana strains has caused the loss of the enzyme (CBDA synthase), which would otherwise compete for the metabolites used as starting material in THCA production,鈥 Hughes said.

Essentially, this means that over thousands of years of cultivation, hemp farmers selectively bred Cannabis sativa into two distinct strains 鈥 one for fibre and seed, and one for medicine. Marijuana has been used medicinally for more than 2,700 years, and continues to be explored for its pharmaceutical potential.

鈥淧lants continue to be a major source of medicines, both as herbal drugs and as pharmaceutical compounds,鈥 Page said. 鈥淎lthough more than 20 plant genomes have been published, ranging from major food crops such as rice and corn, to laboratory models like Arabidopsis, this is the first genome of a medicinal plant.鈥

The researchers expect that sequencing the Cannabis sativa genome will help answer basic questions about the biology of the plant as well as furthering development of its myriad applications. These include strains for pharmaceutical production, high-producing industrial hemp plants, and hemp seed varieties to produce high-quality edible oil. Hemp seed oil is rich in omega 6, an essential fatty acid, and its fibre is used in the production of textiles.

According to the Canadian Hemp Trade Alliance, about 25,000 acres of the crop were sown in Canada in 2010, much of this in Manitoba. Due to hemp鈥檚 association with marijuana, farmers need to be licensed through Health Canada to grow the crop. Canadian medicinal marijuana is currently produced under Health Canada contract with Prairie Plant Systems, a biotechnology company based in Saskatoon.

The article describing the research findings, The draft genome and transcriptome of Cannabis sativa, will be published Oct. 20, 2011 in the BioMed Central open access journal .

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