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October 17, 2011

Scientists characterize barley plant-stem rust spore ‘communication’

Traditional thought holds that a disease-causing organism has to penetrate a plant to initiate resistance. Now, two Washington State University scientists have established that a barley plant recognizes an invader and begins to marshal its defenses within five minutes of an attack.

The discovery, along with the scientists’ successful cloning of barley’s disease-fighting gene and the pathogen’s signaling gene, could help to revolutionize the battle against cereal crop enemies such as stem rust.
Unless carefully controlled, stem rust has the potential to destroy a grower’s entire crop. It has caused the loss of millions of dollars of grain. Meanwhile, new threats are on the horizon. For example, Ug99 is becoming a threat to wheat, posing a new threat to global food security.
Andy Kleinhofs, professor of molecular genetics in WSU’s Department of Crop and Soil Sciences, has been working with assistant research professor Jayaveeramuthu Nirmala to understand the mode of action of Rpg1, a gene that provides barley with resistance to the pathogen that causes stem rust.  The scientists’ latest work involves a deeper understanding of how Rpg1 and the genes that activate it work to trigger resistance to stem rust.
In the course of their investigations, Kleinhofs and Nirmala found that that the plant recognizes the pathogen within five minutes of the spore touching the leaf, before penetration of the leaf takes place.
The plant’s initial reaction to attack is invisible to the human eye, Nirmala said, but she succeeded in monitoring subtle changes in plant chemistry that demonstrated the plant not only recognized it was under attack but was starting to muster its resistance. 

Visible signs of the stem rust spore’s impact come within an hour, when pad-like lesions connecting the spore to the leaf cell begin to appear.
Camille Steber, a research geneticist for the U.S. Department of Agriculture’s Agricultural Research Service at WSU, said Steber said the discovery is a game-changer for plant scientists.
"This is the first example where the lock-and-key of cereal-pathogen response is clearly understood,” she said.
Kleinhofs said, "There is still a lot to be learned,” he added. "As with any new discovery, more questions arise than have actually been answered, but it’s a good start.”


Andy Kleinhofs, professor, Department of Crop and Soil Sciences and School of Molecular Biosciences, 509-335-4389,
Jayaveeramuthu Nirmala, assistant research professor, Department of Crop and Soil Sciences,509-335-5272,

Kathy Barnard, Marketing, News, and Educational Communications, 509-335-2806,

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