Even the most advanced computer is merely a complex arrangement of simple, modular parts that control specific functions. Colorado State University scientists are creating this modularity of computers in plants. They have designed gene "circuits" that control specific plant characteristics like color, size, resistance to drought, etc.
The CSU team have created the gene circuits with the help of the relatively new, interdisciplinary field called synthetic biology. These gene circuits can be easily placed in one organism or the next and made to function. In the present scenario, most of the synthetic biologists work is going on with simple microorganisms, like E. coli or yeast. 
A CSU team led by June Medford, professor of biology, and Ashok Prasad, associate professor of chemical and biological engineering, is doing the same thing, but in the much more complex biological world of plants.
Traditional plant genetic engineering involves inserting or modifying genes that control certain characteristics. Today's plant synthetic biologists are taking a different approach.
"We are quantitatively analyzing the gene parts so we can make predictable functions," Medford said. Using the cell phone analogy, "Apple didn't go and reinvent a circuit to build the new iPhone; they took an existing circuit and tweaked it," she said. "Once you have the quantification, and the device physics of the parts characterized, you can use a computer to tell you how to put them together."
Prasad added that plants in particular, pose a special problem. Not only is the biology of plants much more complicated than single-celled microorganisms, they are also slow to grow and develop. As a consequence, just testing different genetic circuits becomes a major undertaking.
Tackling this problem, they've invented a method of characterizing not one or two, but hundreds of genetic circuits at a time that control plant functions. They first had to create a blueprint for part construction -- the cell parts that make up the eventual circuits. For the testing, they used protoplasts, which are plant cells whose walls have been removed, so they're little blobs of cytoplasm.
The researchers' new method will pave the way to develop and screen hundreds of genetic circuits, opening the door for rapid new developments in plant synthetic biology.
Protoplasts are delicate, though, so the engineers employed mathematical modeling that accounted for all the special properties of each protoplast. Carrying out intensive data analysis and simulations led them to isolate properties of single protoplasts -- an unprecedented achievement.
They demonstrated their method with the plant Arabidopsis, with later validation in the food grain species Sorghum bicolor -- demonstrating their technique with a commercially relevant species.
The scientists were supported by a Department of Energy grant for working on a specific circuit that, when completed, will act like a hard switch that turns on and off a specific genetic function.
Prasad said that this study was a true collaboration in which both sides participated fully in the entire endeavor, and should be a model for collaborations between computational modelers and experimental biologists.
Co-first author of the study was Katherine Schaumberg and co-author was Wenlong Xu. They are both graduate students in biomedical engineering and they handled all the data analysis for the project, and helped develop the mathematical model.
Co-first author and research assistant professor Mauricio Antunes helped develop the experimental platform for the protoplast experiments, while postdoctoral associates Tessema Kassaw and Christopher Zalewski also played crucial roles in experiments and analysis.
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