Potted tobacco plants growing in a college research facility could one day hold the key to rapid Covid-19 antibody tests. Researchers at the University of Victoria in British Columbia, Canada, are inserting the genes of the SARS-CoV-2 (Covid-19) spike protein into the leaves of Nicotiana benthamiana, a relative of the tobacco plant, to see if they can produce the protein at scale for serological test kits.
If successful, the research could lead to mass production of the protein, which is difficult to accomplish in a lab.
“We’re using these plants as biochemical factories to produce large amounts of this specific protein that could be very valuable for serological testing,” says C. Peter Constabel, professor of biology and director for the Centre for Forest Biology at the University of Victoria. “And in order to do this, we need to grow plants in very constant or controlled conditions.”
Conviron plant growth chambers provide the controlled environment the research team needs to accomplish its goals. The researchers moved the plants from the greenhouse to the chambers in the early stages of the project due to premature flowering, Constabel says.
“We thought it might be related to the number of daylight hours,” Constabel explains. “We start new batches of plants each week, and we want each set of plants to be grown exactly the same way, so that plant variability does not become a problem. This includes light levels, photoperiod, and temperature. The greenhouse didn’t provide the type of controlled environment we needed for consistent results.”
Growing up fast
The researchers are growing the plants in 4-inch pots in a Conviron PGR15 reach-in chamber. It’s one of 16 Conviron plant growth chambers in the research facility.
One of the advantages of the system is that it produces fast growth. The researchers have a continuous production operation, meaning each week they start new plants from seed in the chambers and test plants of different sizes to determine the optimal age for generating the spike protein.
“Within a week of the transformation experiment, if it works, we’ll see the protein, so it’s very, very fast, and that’s the beauty of it,” Constabel says.
As the project scales, the research team may begin using an additional chamber to grow the tobacco plants. If researchers can detect a significant amount of the spike protein in the leaves, the next step is to harvest the plants. They would then grind the leaves in a blender and purify the spike protein using a chromatographic separation process. After they get a pure protein, it will be sent to their biotech partner who is developing the rapid-test technology.
The Centre for Forest Biology has been using the Conviron plant growth chambers for about 30 years, Constabel says. The department has retrofitted the chambers with LED lights, which help to control the spectral properties better than fluorescent lights but otherwise there has not been a need to make significant modifications to the units.
The plant growth chambers have provided a reliable, controlled environment for a wide range of projects over the years. This includes current research on poplar saplings and tests with hydroponic containers to identify and understand what type of chemicals are released from roots.
“The most critical thing the chambers provide is that we can control the photoperiod and temperature, which are the standard things we need to determine plant behavior and plant growth,” Constabel says.
If the project with the tobacco plants proves to be successful, the plant-growth chambers could play a larger role in the next phases of the project.
“I think it’s going to be important if we decide we need to alter growth conditions to improve the yield of recombinant protein,” Constabel says. "Being able to control all environmental factors and doing so in a reproducible way is critical for our research”.