Researchers have developed a rice plant that is able to efficiently fight off a range of pathogens, by connecting what is essentially a tunable amplifier to its immune system. Scientists have long tried to develop crops that can fight off diseases and microbes, to help alleviate the need for pesticides. However, most of these have so far only provided protection against a single disease at a time.

Jonathan Jones, who studies plant defense mechanisms at the Sainsbury Laboratory in Norwich, UK, said:

“For as long as I have been in this field, people have been scratching their heads about how to activate a defense system where and when it is needed. It is among the most promising lines of research in this field that I have seen.”

Without a bloodstream to circulate immune cells, plants use receptors on their cells to identify microbes, signaling a release of antimicrobial compounds. In theory, scientists could boost immune responses by identifying the genes that spark this immune response, and increasing their level of activity. Scientists have succeeded in using genes, called NPR1, to boost plant immune systems. However, this so far has worked so well that the robust immune reactions have made the plants less viable for agricultural – similar to the way a human with a high fever are less productive.

To make this technique useful in an agricultural context, scientists would need to better control these immune responses, so they only respond when the plant is under attack, otherwise allowing the plants to grow normally.

Two papers published this week in Nature, by a team at Duke University led by Plant biologist Xinnian Dong, working with researchers at Huazhong Agricultural University in Wuhan, China, discussed the discovery and application of this method.

Dong discovered a system that uses messenger RNA molecules to encode an immune activating protein, from the commonly studied thale cress plant (Arabidopsis thaliana), which are called TBF1. It quickly translates into TBF1 proteins, which spark a system of immune responses. Dong discovered that a segment of the DNA, which she calls the “TBF1 cassette,” acted as a control switch for the immune response. Dong essentially copied the TBF1 cassette and pasted it in front of the NPR1 genes in rice plants.

This process yielded a strain of rice that can quickly turn its immune responses on and off, in bursts with the power to defend it from pathogens, but that are brief enough to allow the plants to grow in a normal way.

The researchers tested their rice strain by inoculating its leaves with pathogens. The modified rice confined the infections to small areas, while the infections spread rapidly in the wild rice plants.

“These plants perform very well in the field, and there is no obvious fitness penalty, especially in the grain number and weight,” said Dong.

One of the pathogens they tested with, called rice blast disease, causes an annual loss of 30 percent of the global rice crop.

Though further testing and development is required, the new strain could someday help farmers in the developing world avoid this loss and others, increasing the food supply worldwide.

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