Plant pathologists are developing methods to study plant defenses against viruses

A group of plant pathologists at Texas A&M AgriLife Research has developed a surprisingly simple approach to studying the complex interactions between plants and viruses. They hope the breakthrough will make improving plant resistance faster and easier and shed light on the evolutionary arms race between plants and their viruses.

Viral infections account for nearly half of known plant pathogens and cost producers worldwide approximately $30 billion each year. For decades, scientists have been researching how plants defend themselves against viruses and how they can strengthen their defense system.

To clarify key components in this system, researchers at Texas A&M AgriLife have developed an innovative approach that uses a modified plant virus to simulate infection while acting as a sensor for the plant's resistance response.

Herman Scholthof, Ph.D., professor emeritus in the Department of Plant Pathology and Microbiology at the Texas A&M College of Agriculture and Life Sciences, led the study published in PNAS Nexus presents their novel approach – the final study of his career as a plant virology researcher.

The three-part approach to identifying crucial genes for plant defense

With their new technique, the researchers followed a three-stage approach: infect, switch off, detect.

First, they simulated infection of plants with a modified virus that expresses a green fluorescent protein. The fluorescent protein is important because it gives scientists a way to easily see whether the virus has been able to multiply uncontrollably.

Next, specific parts of the plant's RNA silencing pathway, its defense system against viral infections, were targeted and inactivated by gene-editing materials delivered by the same virus. Finally, the researchers checked whether the virus had accumulated in the plant, which informed the team whether or not the targeted, inactivated genes were crucial in preventing virus replication.

By observing where and how much green fluorescence was produced – a visual cue that is easy for scientists to measure – the researchers were able to tell whether the plant's defense mechanism was working or not.

If the plant's defenses were active and responding to the virus infection, there would be little virus accumulation or green fluorescence. However, when the plant's defenses are not active because one or more of the crucial genes needed to stop a virus are attacked and silenced, the plant leaf glows fluorescent green as the virus reproduces.

Using this approach, Scholthof says the team was able to target several key genes in the RNA silencing pathway and identify those that are essential for preventing virus replication. They were also able to confirm their previous findings that some often overlooked genes are crucial for plant defense against viruses.

Scholthof said he viewed their study as a proof of concept, demonstrating a new method for rapidly screening plant genes involved in antiviral defense. By introducing the gene editing system directly into plant cells using a viral vector, the method avoids time-consuming aspects of other methods.

“This represents a significant advance in understanding the complexities of plant-virus interactions and could ultimately support more resilient agriculture,” he said.

The final chapter of a research career

Scholthof has been a professor and researcher at Texas A&M AgriLife for nearly 30 years. He said this latest research study was the perfect book-end to his career, as it summarized many of the focus areas he has returned to over the years, such as RNA silencing and viral gene vectors.

A significant portion of the research was conducted by April DeMell, the study's lead author and a former graduate student in Scholthof's lab.

“I was surrounded by very talented people – technicians, undergraduate and graduate students, postdoctoral fellows and visiting scientists – who were responsible for carrying out much of the work in the lab,” he said. “Training people to become successful is one of the most rewarding aspects of this profession.”

Scholthof and his wife, Karen-Beth Scholthof, professor emerita in the Department of Plant Pathology, both retired in July and recently moved to Colorado. But neither has given up on educating the world about plant pathology.

Instead, Scholthof begins a new chapter – both literal and figurative – in the form of a book that aims to shed light on the fascinating world of virology to engage the next generation in its wonders and applications.

“After teaching plant virology for over 30 years, it’s more than just the subject you teach,” he said. “You find examples, analogies and explanations that other people don’t find. Who knows? I have dedicated my career to this.