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Crop Biotech Update

Research Reveals How Ancient Viruses Got Cannabis High

November 28, 2018

A study conducted at the University of Toronto (UT) has produced the world's first chromosome map of cannabis, revealing the plant's evolutionary past and points to its future as potential medicine. The researchers from UT's Donnelly Centre found that THC and CBD, bioactive substances produced by cannabis and sought by medical patients and recreational users, sprung to life thanks to ancient colonization of the plant's genome by viruses.

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 of late for its medicinal potential.

The enzymes making THC and CBD are encoded by THCA and CBDA synthase genes, respectively. Both are found on chromosome 6 of the 10 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.

For more details, read the news release from Connelly Centre.