Biosensor detects early fungal outbreaks, advances plant biotechnology

A new biosensor developed at the Department of Energy's Oak Ridge National Laboratory detects the emerging presence of fungus on plants at the molecular level, paving the way for next-generation crop protection and the development of stress-tolerant plants. The innovation advances technology for the U.S. agricultural and biomanufacturing sectors.

The sensor identifies fungal outbreaks in near-real time, well before plants show visible symptoms, enabling faster, more precise treatment than traditional monitoring methods. The technology, described in the Plant Biotechnology Journal, can also signal when beneficial plant-microbe interactions occur, helpful to plant scientists as they engineer stress-tolerant feedstock crops for the production of advanced chemicals and materials.

For example, the biosensor can help detect an emerging outbreak of Septoria canker, a fungal pathogen that causes stem canker disease in some poplar trees, a plant of interest as a perennial energy crop.

The biosensor was created using split protein segments called inteins, along with attached biomarkers to detect the presence of chitin, a core structural component of fungal cell walls. When chitin is present, the protein fragments reassemble and produce a fluorescent glow, letting researchers see the moment when a plant recognizes a microbial signal.

"These tools change how we approach functional genomics, helping us understand how genes work together to control plant systems," said Paul Abraham, R&D staff scientist and lead for the DOE Secure Ecosystem Engineering and Design Scientific Focus Area (SEED SFA), which supported the project. "Our biosensors detect and help us understand how key events unfold as plants grow, including their interaction with the environment and, in this case, with influential microbes. By enabling very early detection, the biosensor allows us to go in and characterize the molecular events surrounding the interactions."

By functioning as a widely adaptable bioengineering tool, the sensor can be modified to identify and study other signaling molecules called ligands that are given off by microorganisms, which in turn trigger plant responses. The ability to enable faster, automated screening of ligands that interact with plant receptors gives scientists new insight into these signaling pathways that are critical to plant immune response, said Xiaohan Yang, project lead in ORNL's Biosciences Division.

The platform can also be modified to study protein-protein interactions inside a living cell by attaching the split inteins to different proteins of interest and tracking whether they re-combine and trigger fluorescence, Yang said. These interactions are likewise essential to plant immunity - a key focus area for researchers developing plants resistant to disease or other stressors.

The invention builds on ORNL's leadership in plant systems biology, developing molecular tools to better understand and engineer complex biological processes. The lab's biotechnology toolbox includes sensors that can:

• detect the activity of CRISPR gene editing tools in organisms, using the naked eye and an ultraviolet flashlight
• visualize and track RNA activity and gene expression in living plants in real time.

Other ORNL scientists collaborating on the project are Bal Maharjan, Van Nguyen, Jerry Parks, Tomás Rush, Carrie Eckert and Jay Chen, along with first author Brian Boone, formerly with ORNL and now at Western Carolina University. The SEED SFA is a project of the DOE Office of Science Biological and Environmental Research program.

UT-Battelle manages ORNL for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. - Stephanie Seay