Rice is an important staple crop, providing nearly a quarter of the calories consumed by humans worldwide. Diseases caused by bacterial or fungal pathogens can result in the loss of 80 percent or more of a rice crop, presenting a significant problem for rice farmers and plant scientists.

Foundation grantees at Duke University have successfully developed a novel method that increases disease resistance in rice without decreasing yield.

Decades of research into the plant immune response have identified components that can be used to engineer disease-resistant plants. However, their practical application to crops is often limited by an active defense response, which reduces yield.

"Immunity is a double-edged sword," said lead author Xinnian Dong, a Howard Hughes Medical Institute-Moore Foundation Plant Biology Investigator and professor of biology at Duke. "There is often a tradeoff between growth and defense because defense proteins are not only toxic to pathogens but also harmful [to themselves] when overexpressed. This is a major challenge in engineering disease resistance for agricultural use because the ultimate goal is to protect the yield."

Previous studies have focused on altering the DNA sequence elements of a gene. These elements are known as promoters, and they act as switches that turn on or off a gene’s expression. By attaching a promoter that gives an "on" signal to a defense gene, a plant can be engineered to be highly resistant to pathogens, though at a cost to growth and yield. These costs can be partially alleviated by attaching the defense gene to a targeted promoter that turns on in the presence of pathogen attack.

Now, a team of researchers led by Dong have developed a strategy to add an additional layer of control for the engineering of disease-resistant crops with minimal yield costs. They turned to newly discovered sequence elements to help address this problem. These sequence elements act on the intermediate of a gene, or messenger (called RNA, a molecule similar to DNA). This regulation results in tighter control over a crop’s defense response, and minimizes the lost yield associated with enhanced disease resistance.

The authors say their flexible strategy has many advantages, as it is broadly applicable to a variety of crop species against many pathogens, not just rice. What’s more, since this strategy involves activating a plant’s defenses, it may also reduce the use of pesticides on crops and reduce environmental impact.

"This work demonstrates the power of basic science to impact society," said Moore Foundation program officer Gary Greenburg, Ph.D. "By studying a basic mechanism in plants for the past 20 years, Dr. Dong has developed a way to tune the plant immune system to fight disease with important real-world consequences and illuminated a path to controlling plant disease without pesticides."

Read the article published in Nature, and watch a video about disease resistance in plants


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