Researchers at Colorado State University have developed a tool that can be used to switch a plant's key genetic traits on or off at will. The breakthrough was recently published in ACS Synthetic Biology and represents the first time that a synthetic genetic "toggle switch" has been used in a full-grown plant.
Synthetic biologists design and build new segments of DNA that can then be inserted into living organisms to work like circuits in electronics or a computer. Just as a switch is used to turn a lightbulb on or off in an electric circuit, the team's "toggle" turns genes on and off when an external signal is applied. Up until now, the genetic toggle switch has only been used in single-celled organisms such as bacteria. The work at CSU is led by professors June Medford from the Department of Biology and Ashok Prasad from the Department of Chemical and Biological Engineering.
Medford said the interdisciplinary research has plenty of practical applications, particularly in agriculture where a switch could be used to better time the ripening of fruit, for example.
She added that any number of traits could eventually be regulated with this tool. The challenge is inserting it into fully developed living organisms.
"The multicellular nature of a plant – their roots, tissues, vegetative and reproductive organs- makes it a complex challenge that we are finally able to overcome," she said. "This work is a promising initial step to programing plants to do all sorts of useful things that were not possible before."
The paper describes the team's work to synthesize relevant plant DNA parts and then design a potential genetic "toggle" system around the two key genes within them using mathematical modeling. This approach helped the team to mix and match possible combinations on the computer, until they found an effective combination. From there, the team began transforming plants with the chosen DNA sequences and tracked results over a 12-day period to quantify the changes.
Medford said it was a long and iterative process towards the proof of concept the paper now demonstrates.
"As biologists, we understand biology really well, and we partner with folks like professor Prasad and his team who are experts at developing the algorithms – this allows us to find the key signals amid the noise," said Medford. "This project is a true marriage between quantitative research and mathematical modeling to predictably engineer a plant's abilities for any number of needs. Our work also opens the possibility that in the future, genetic circuitry design like this could be automated through machine learning speeding the process."
Notably, the research shows that these circuits function across the whole plant and can be used to regulate shoots and cells across different parts of the life cycle. Prasad said that means these switches could be used to engage different plant functions in support of food security or materials development.
"In the face of unpredictable and unseasonable climates farmers could control the state of their crops by turning 'on' a switch that promotes drought tolerance. Or one that helps plants like pumpkins grow earlier in the season and then retain size and nutrition," Prasad said. "The applications for this breakthrough are nearly endless for humanity and the environment."
