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Scientists Show How Plant Pathogen Dampens Host Immune Response


By Sarah Nightingale

The bacterial pathogen Xylella fastidiosa (Xf)dampens the immune response of the plants it infects, allowing it to go undetected for long enough to cause disease. A team led by Caroline Roper, an associate professor of plant pathology, has published a paper in Nature Communications describing how this happens and how it might be prevented.

Xf is the major threat to viticulture in California, the U.S. and worldwide. It causes a lethal disease called Pierce’s disease and affects wine, raisin and table grapes, which are a multibillion dollar industry in California alone. The pathogen can also affect many other hosts including citrus, olives and almonds.

Lipopolysaccharides (LPS), which are found in the cell walls of many bacteria, trigger strong immune responses in plants and animals. To subvert this response, many pathogenic bacteria have evolved ways to weaken LPS-triggered immune responses. Roper’s group found that a long terminal polysaccharide chain (known as the O-antigen) present in Xf LPS enables it to delay recognition by grapevine hosts. They also showed that pretreating grapevine with LPS that lacked the O-antigen enabled it to better resist Xf infection.

“We are working on understanding the molecular basis of the pre-treatment and its effects to determine if we can leverage this information for disease control,” Roper said.

The title of the paper is “Lipopolysaccharide O-antigen delays plant innateimmune recognition of Xylella fastidiosa.” Jeannette Rapicavoli, who earned her Ph.D. in Roper’s lab at UCR, was first author on the paper. Other authors are Roper and Claudia Castro from UCR; and Barbara Blanco-Ulate, Rosa Figueroa-Balderas, Abraham Morales-Cruz and Dario Cantu from UC Davis; and Artur Muszyński, Parastoo Azadi and Justyna Dobruchowska from the University of Georgia.


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