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Thursday, December 2, 2021

UC Davis researchers identify rice protein that moderates disease resistance

Scientists at UC Davis have discovered a rice protein that plays a major role in moderating the resistance to infectious disease, a discovery that may have important medical and agricultural applications around the world.

A study led by plant pathology professor Pamela Ronald identified the protein XB15, a major player in the rice plant’s immune system that stops the immune response from overreacting and damaging the plant.

The Ronald lab has made similar discoveries in the past. In 1995, researchers in the lab found a rice protein that acts as a pathogen recognition receptor. These receptors are found in nearly all higher life forms and are essential to control the organism’s immune system. This specific receptor, called XA21, controls how animals and plants respond to a disease.

Although extremely important in fighting off diseases, if these receptors are not regulated, they could lead to various diseases, including cancer in humans.

It turns out that the recently discovered XB15 works hand in hand with the recognition receptor XA21. Known as a negative receptor, the protein XB15s purpose is to regulate the immune system and make sure that the immune response is truly necessary.

The Ronald lab has shown that an altered version of the XB15 protein has a better resistance to the bacterial leaf blight disease, a serious bacterial disease in rice. However, if the XB15 protein is produced excessively in plants also carrying the XA21 resistance gene, it can then compromise the immune response to fight off the disease.

“Rice, in general, can be very susceptible to infectious disease like bacterial leaf blight, which damages the crop and can eventually lead shortages in developing countries,Ronald said.

Both environmental factors and disease can severely affect the season’s crop of rice. Floods and other environmental stresses can decimate the rice crop. As much as 60 percent of crops can be destroyed by the disease alone, which in turn threatens the food source of nearly three billion people, according to the International Rice Research Institute’s website.

Rice is grown in more than 89 countries around the world and in six of the seven continents. Genetically altered rice plants have been grown in temperatures naturally too cold and too warm to survive.

According to the IRRI, rice’s importance lies in its easy ability to cook, store, and be purchased inexpensively. Many countries heavily depend on it as a staple food.

Currently, the best method to combat diseases is to spray pesticides on the crops. The Ronald lab’s goal is to find better alternative solutions.

“By gaining a better understanding of how resistance is conferred in plants, we will be able to further develop rice plants through breeding or genetic engineering with the goal of reducing the use of pesticides,said Becky Bart, a graduate student in the Ronald lab, in an e-mail.

For this reason, this discovery is vital for the development of more productive and hardier plants that could meet the worldwide demand for rice, Ronald said.

Though the protein’s discovery has an impact on agricultural research, the identification of the XB15 protein has medical implications as well. Both humans and plants have immune systems to fight off infectious disease and use very similar proteins. An understanding of a plant’s immune system response could potentially be translated to humans.

“This protein lends us a better understanding of how the immune system works and how it’s regulated in higher organisms,Ronald said. A more in-depth comprehension would lead to better treatments and medications for humans.

NICK MARKWITH can be reached at features@californiaaggie.com.

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