Two Canadian researchers hope their work - mapping the cannabis sativa genome - will get rid of the stigma they say surrounds the cultivation of hemp and marijuana in Canada.
The University of Saskatchewan's Jon Page and the University of Toronto's
Tim Hughes hope other scientists will use their work to develop marijuana as a legitimate medical ingredient, and hemp as a high-quality, fastgrowing crop.
"It's a useful plant," Page told Postmedia News on the phone from Saskatoon.
"You can eat it, you can build with it, you can use it as medicine ... but, because of its reputation, it's hard to get funding to work with it."
Using genome sequencing technology, Page and Hughes found that, through years of cultivating cannabis, farmers changed the molecular makeup of the plant itself.
As with bulldogs and basset hounds, marijuana and hemp are different breeds of the same species (cannabis sativa), but marijuana contains much more THC (the medicinal ingredient) than does hemp, the fibres of which can be used to make everything from bricks and strong rope, to fibreglass and plastic-like material used to build cars, like the Canadian-made Kestrel.
In short, the THCA synthase gene - or the stuff that gets you high - is turned on in marijuana, but switched off in hemp.
Page and Hughes are the first researchers to map the cannabis genome, making it the 22nd plant and the first medicinal plant to be mapped in this way.
But the plant biochemist and the molecular biologist say research into best practices for farming the fast-growing, multi-purpose plant has lagged behind other cash crops, such as corn, rice and wheat, because of sticky laws and an unfair reputation.
"There's just a stigma against it, so it's not being utilized," said Hughes, speaking from a conference in Barcelona, Spain.
However, the research, which will be published Thursday in the openaccess journal Genome Biology, could be used by hemp enthusiasts to push for fewer restrictions.
Page says Health Canada - which is responsible for regulating hemp cultivation in this country - seems to have struck a good balance by allowing licensed farmers to grow the crop since 1998, lifting a 60-year ban.
In terms of its medicinal use, Health Canada grants access to marijuana to those "who are suffering from grave and debilitating illnesses," such as epilepsy, multiple sclerosis, arthritis, HIV/AIDS, spinal cord injury or various forms of cancer.
Today, governmentgrown medicinal marijuana in Canada contains as much as 13 per cent THC, whereas hemp plants contain less than 0.3 per cent, rendering hemp virtually useless for "recreational purposes," said Page.
Hemp was raised for its fibre in the United States until legislation outlawed all cannabis plants because they contain THC.
Some states have since pushed to allow farmers to grow hemp, but Page says the legal climate south of the border makes a Canadian-like system unlikely in the near future.
According to the Canadian Hemp Trade Alliance, about 25,000 acres of the crop were sown in Canada in 2010 - mostly in Manitoba.
The Vancouver Sun 20th Oct 2011
Editorial about the Research
If Genome Biology had been launched today, instead of 11 years ago, it might well have been given the alternative title of "Transcriptome Biology".
While Genome Biology captured the millennial zeitgeist of genomics brought about by the project(s) to sequence the human genome, the breathtaking progress of this field in the intervening decade has brought us to a new frontier: the transcriptome.
The development of RNA-seq, which applies high-throughput next-generation sequencing technology to cDNA generated from RNA samples, has resulted in an explosion of transcriptome sequences. Not only does RNA-seq benefit from higher sensitivity than microarrays, it also does not require the a priori knowledge needed for constructing chips; this flexibility has infused the transcriptome explosion with a biologically diverse character and encompassed many species not well covered by commercially available microarrays.
Species such as Cannabis sativa, a plant with a 'split personality', whose Dr Jekyll, hemp, is an innocent source of textiles, but whose Mr Hyde, marijuana, is chiefly used to alter the mind. Until now, Cannabis sativa was not one of the many species whose genome had been published during Genome Biology's lifetime. In common with many plants, genome assembly of cannabis DNA sequence is technically challenging, and so the publication a 534 Mbp draft genome in this month's issue is in itself a landmark achievement.
However, a comparison of the draft genome, which is that of the Purple Kush marijuana strain, with genes in the cannabinoid biosynthetic pathway in hemp strains did not point to any variants likely to result in a functional difference in the production of THCA - the chemical underlying marijuana's psychoactivity. But, as with Genome Biology's recent article on the kangaroo, a fruitful decision was made to analyze cannabis's transcriptome while completing its genome project.
Gene expression levels observed in the plant's flower made the likely reason for phenotypic differences between hemp and marijuana strikingly apparent. While transcripts for the THCA synthase enzyme were abundant in marijuana, they were barely detectable in hemp. Similarly, an enzyme that removes a precursor from the THCA synthesis pathway was highly expressed in hemp but not detectable in marijuana.
So it seems that the transcriptome is how hemp got high - or maybe how marijuana came 'down'. Either way, it is clear that without complementing a genome with functional information, such as the transcriptome, the true meaning of a DNA sequence will largely remain unknown.
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