Cannabis, a plant that is gaining increasing attention for its wide range of medicinal properties, contains dozens of compounds known as cannabinoids.
One of the most well-known cannabinoids is cannabidiol acid (CBD), which is used to treat pain, inflammation, nausea, and more.
Cannabinoids are produced by trichomes, small spiky bumps on the surface of cannabis flowers. Beyond this fact, scientists know very little about how cannabinoid biosynthesis is controlled.
Yi Ma, research assistant professor, and Gerry Berkowitz, professor of the Faculty of Agriculture, Health and Natural Resources He received funding through the US Department of Agriculture’s National Research Initiative to uncover the underlying molecular mechanisms behind trichrome development and cannabinoid synthesis.
Berkowitz and Ma, along with former graduate students Samuel Haiden and Peter Apicella, discovered transcription factors responsible for trichome initiation and cannabinoid biosynthesis. Transcription factors are molecules that determine whether a part of an organism’s DNA will be transcribed into RNA and therefore expressed.
In this case, transcription factors cause the epidermal cells of the flowers to transform into trichomes. The team’s discovery was recently published as a lead article in plants. Research related to trichome a was also published Direct plant. Because of the potential economic impact of the gene, UConn has introduced a provisional patent application on the technology.
With this new grant, the researchers will continue to explore how these transcription factors play a role in trichome development during flower maturation.
Berkowitz and Ma will clone the promoters (the part of DNA that transcription factors bind to) of interest. They will then put the promoters into the cells of a model plant along with a copy of the gene that makes fireflies light up, known as firefly luciferase; luciferase is fused to the cannabis promoter so that if the promoter is activated by a signal, the luciferase reporter will generate light. “It’s an ingenious way to assess the signals that orchestrate cannabinoid synthesis and trichome development,” says Berkowitz.
Researchers will load the cloned promoters and luciferase into a plasmid. Plasmids are circular DNA molecules that can replicate independently of chromosomes. This allows scientists to express genes of interest even though they are not part of the plant’s genomic DNA. They will deliver these plasmids to plant leaves or protoplasts, plant cells without a cell wall.
When the promoter controlling luciferase expression comes into contact with the transcription factors responsible for trichome development (or triggered by other signals such as plant hormones), the luciferase “reporter” will produce light. Ma and Berkowitz will use an instrument called a luminometer, which measures how much light is coming from the sample. This will tell researchers whether the promoter regions they are looking at are controlled by transcription factors responsible for increasing trichome development or modulating genes that code for cannabinoid biosynthetic enzymes. They can also tell if promoters respond to hormonal signals.
In previous work underlying the rationale for this experimental approach, Ma and Berkowitz along with graduate student Peter Apicella found that the enzyme that makes THC in cannabis trichomes may not be the critical limiting step that regulates the production of THC, but rather the generation of the THC precursor. Production (and CBD) and transport facilitated by precursor transport in the extracellular bulb could be key determinants in the development of cannabis strains with high levels of THC or CBD.
Most cannabis farmers grow hemp, a variety of cannabis with naturally lower THC levels than marijuana. Currently, most hemp strains that have high levels of CBD also contain unacceptably high levels of THC. This is likely because hemp plants still produce the enzyme that produces THC. If the plant contains more than 0.3% THC, it is considered illegal at the federal level and, in many cases, must be destroyed. A better understanding of how the plant produces THC means that scientists could selectively remove the enzyme that synthesizes THC using genome editing techniques such as CRISPR. This would produce plants with lower or no THC levels.
“We anticipate that the fundamental knowledge gained can be translated into new genetic tools and strategies to improve the cannabinoid profile, help hemp farmers with the common problem of overproducing THC, and benefit human health,” say the researchers.
On the other hand, this knowledge could lead to the production of cannabis plants that produce more than one desired cannabinoid, making it more valuable and profitable.
In addition to sharing these findings with scientists, industry and cannabis growers, the researchers will incorporate this new knowledge into UConn courses on cannabis horticulture.
This grant will also support the training of undergraduate students interested in cannabis research, providing them with the skills to enter the workforce.
This research was bolstered by preliminary data that Berkowitz gathered through a grant from the OVPR Research Excellence Program. For more information about marketing opportunities, contact techcomm@uconn.edu.
keep going UConn CAHNR in social networks