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research update


UCR STRATEGIC COMMUNICATIONS Wenbo Ma, an assistant professor of plant pathology and microbiology at the University of California, Riverside. How do plants fight disease?


Breakthrough findings by UC Riverside plant pathologist offer a clue.


By Iqbal Pittalwala H


ow exactly bacterial pathogens cause diseases in plants remains a mystery and continues to frustrate scientists working to solve this problem. Now , a young plant pathologist at the University of California, Riverside, has performed research on the soybean plant in the lab that makes major inroads into our understanding of plant-pathogen interactions, a rapidly developing area among the plant sciences.


Her breakthrough research can help scientists come up with effective strategies to treat crops that have succumbed to disease or, when used as a preventive measure, to greatly reduce their susceptibility to disease.


In a paper published in the March issue of the journal Cell Host & Microbe, Ma, an assistant professor of plant pathology and microbiology, and her colleagues show that the bacterial pathogens target isoflavones, a group of compounds in plant cells that defend the plant from bacterial infection, resulting in a reduction in isoflavone production.


First, the pathogens inject virulence bacterial proteins, called HopZ1, through needle-like conduits into the plant cells. These proteins then largely reduce the production of the isoflavones and promote disease development. However, by sensing the presence of HopZ1, the plants mount a robust resistance against the pathogen, including the production of a very high amount of isoflavones.


At this point, the pathogen must come up with new strategies by either changing the kind of proteins it injects into the plant, not injecting any proteins at all, or injecting virulence proteins in a way that helps them escape detection by the plant. In this


18 British Columbia Berry Grower • Summer 2011


way, the virulence bacterial proteins and the plant host engage in an endless “arms race.”


“One question we are still trying to answer is how at the molecular level the bacterial virulence proteins promote disease,” Ma said. “Some scientists have shown that these proteins block signaling transduction pathways in the plant, which eventually weakens plant immunity. “We are introducing a fresh perspective on this topic, namely, that the pathogens evolved strategies to directly attack the production of plant antimicrobial compounds, such as isoflavones, thus compromising the plant’s defense mechanism.” According to Ma, her results can be extrapolated to understand how plants defend themselves when attacked by pathogens. She is pleased to be resuming research first studied by UC Riverside’s Noel Keen, the late plant scientist and a pioneer in molecular plant pathology, who did fundamental groundbreaking work on


understanding how isoflavones and


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