Rice plant engineered with a ‘tunable’ immune system could fight multiple diseases at once

Last changed: 19 May 2017


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by Mistra Biotech

"Farmers are constantly spraying pesticides on their crops to combat an array of viral, bacterial, and fungal invaders. Scientists have been trying to get around these chemicals for years by genetically engineering hardy plants resilient to the array of diseases caused by microbial beasties. Most attempts so far confer protection against a single disease, but now researchers have developed a rice plant that fights multiple pathogens at once—without loss to the crop yield—by hooking up a tunable amplifier to the plant’s immune system."

"Plant biologist Xinnian Dong at Duke University in Durham, North Carolina, has been studying one of these genes for 20 years—a “master regulator,” she says, of plant defense. The gene, called NPR1 in the commonly studied thale cress plant (Arabidopsis thaliana)—a small and weedy plant topped with white flowers—has been a popular target for scientists trying to boost immune systems of rice, wheat, apples, tomatoes, and more. But turning up NPR1 works too well and “makes the plants miserable, so it is not very useful for agriculture,” Dong says.

To understand why, consider the human immune system. Just as sick people aren’t very productive at work when their fever is high, plants grow poorly when their own immune systems are overloaded. Likewise, keeping the NPR1 gene turned on all the time stunts plant growth so severely there is no harvest for the farmers.

To make NPR1 useful, researchers needed a better control switch—one that would crank up the immune response only when the plant was under attack, but otherwise would turn it down to let the plants grow. Two papers published in Nature this week from Dong’s team at Duke, in collaboration with researchers at Huazhong Agricultural University in Wuhan, China, describe the discovery and application of such a mechanism."

"The researchers demonstrated that their rice was superior compared with regular rice by inoculating their leaves with the bacterial pathogens that cause rice blight (Xanthomonas oryzae pv. oryzae) and leaf streak (X. oryzae pv. oryzicola), as well as the fungus responsible for blast disease (Magnaporthe oryzae). Whereas the infections spread over the leaves of the wild rice plants, the engineered plants readily confined the invaders to a small area. “These plants perform very well in the field, and there is no obvious fitness penalty, especially in the grain number and weight,” Dong says." - Ryan Cross 18/5



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