By Celeste Baumgartner
KNOXVILLE Tenn. – Imagine this: a potato plant whose leaves can produce a green glow in the presence of harmful radiation levels. Rob Sears, a doctorate student at the University of Tennessee (UT) Herbert College of Agriculture, has developed such a plant.
“At Fukushima Power Plant (where there was a nuclear disaster in 2011) they had mechanical sensing stations set around the plant in case of emergency,” Sears said. “When the tsunami and earthquake happened, power sources for those mechanical sensors failed.”
The plant sensor, maybe eight rows of potato plants, could be in addition to mechanical sensors in case of a mechanical failure, Sears said. Since potatoes are grown across the world in hospitable and adverse climates, they are the ideal plant for this research.
The potato is ideal for a radiation phytosensor (an environmental watchdog) because it reproduces by producing tubers, Sears said. This means when you place a potato radiation phytosensor in the landscape it will remain in the same place and each year will send up new shoots that are genetically identical to the original sensor plant.
Nuclear energy is coming to the forefront of the carbon-neutral energy efforts, Sears explained. In Tennessee this is evidenced by the TVA’s Advanced Nuclear Solutions plan; Illinois is the no. 1 state in the country for nuclear power production.
As nuclear energy continues to be used around the world, there is an increased demand for effective and easily accessible radiation detection methods. Phytosensors are affordable, easy to interpret, and require no mechanical maintenance. They have the potential to improve the safety and well-being of workers and residents who are near radiation sources.
“If we are going to be expanding our nuclear capabilities, we should also be expanding our sensing equipment so we know if there is a problem,” Sears said. “A plant radiation sensor would be self-sufficient, cheaply scalable across the landscape, and directly reflect the impact of radiation on the environment making it a good option for future monitoring strategies.
“We have co-opted the plant’s DNA repair system to produce a green, fluorescent protein, in addition to carrying out repair, which we can see using specialized camera equipment,” he explained. “Similar equipment is used to take measurements of crop performance from drones or satellites (typically measuring chlorophyll content).”
However, while Sears has focused on the green, fluorescent protein in potatoes, his laboratory has produced other plants that work as sensors. Plants are ideal as sensors he said, because they have to stay in one place and can’t run away like animals. They have a response system that is finely tuned for a variety of chemicals and other stressors. That makes them ideal for environmental sensors.
“The nice thing about this technology, when you are thinking about how the genetics works, they are transferrable to any plant species,” he said. “Depending on how resistant the plant species is, it would work just about the same in any plant species.”
Potatoes are not going to be around in the winter, he said. But pine trees could be engineered in the same way.
Sears said his project would not have been possible without the support of Dr. C. Neal Stewart Jr., professor in the UT Department of Plant Science, and Dr. Scott C. Lenaghan, professor in the UT Department of Food Science, who both served as faculty partners in the study. The study was funded by the Defense Advanced Research Projects Agency (DARPA).
Said Stewart: “I consider our radiation phytosensor the crown jewel of DARPA’s Advanced Plant Technologies program. From the day I coined the word (phytosensors) over 20 years ago, I imagined using such an engineered plant to sense dangers and communicate the hazard to humans.”
Added Lenaghan: “The radiation phytosensor demonstrates the potential of synthetic biology to engineer plants as ‘devices’ that can impact not only agriculture but also provide valuable tools for increasing the safety of the built environment.”
So, what’s next? The next steps would involve more testing to improve the design of the sensor, Sears said. Also, the current sensor requires specialized equipment to “read” the signal. Future designs would use a unique reporter that is visible to the human eye. An example would be using a gene called “RUBY” rather than the fluorescent protein they currently use. RUBY would turn the plant beet-red in response to radiation.