History Is Key Factor in Plant Disease Virulance

The virulence of plant-borne diseases depends not just on the particular strain of a pathogen, but on where the pathogen has been before landing in its host, according to new research results. Scientists from the University of California System and the U.S. Department of Agriculture's Agricultural Research Service (USDA ARS) published the results on April 18, 2012 in PLoS ONE. The study demonstrates that the pattern of gene regulation--how a cell determines which genes it will encode into its structure and how it will encode them--rather than gene make-up alone affects how aggressively a microbe will behave in a plant host. The pattern of gene regulation is formed by past environments, or by an original host plant from which the pathogen is transmitted. "If confirmed, this finding could add a key new dimension to how we look at microbes because their history is going to matter--and their history may be hard to reconstruct," said Dr. Matteo Garbelotto, an environmental scientist at the University of California, Berkeley, and co-author of the paper. Epigenetic factors--for example, gene regulation mechanisms controlled by diet or exposure to extreme environments--are well known to affect the susceptibility of humans to some diseases. The new study is the first to show a similar process for plant pathogens. "Sudden oak death, for example, is one of many pathogens that seemingly came out of nowhere to ravage the forests of California," said Sam Scheiner, a director of the National Science Foundation's (NSF) Ecology and Evolution of Infectious Diseases (EEID) program, which funded the research. "This study shows that such sudden emergence can happen through rapid evolution, and may provide clues for predicting future epidemics." The EEID program is a joint effort of NSF and the National Institutes of Health.
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