Plant proteins block invading microbes

DAVIS, Calif., July 7 (UPI) -- U.S. and Danish scientists say they've identified proteins that prevent bacteria from infecting a plant's leaves.

The researchers at the University of Copenhagen, the University of California-Davis and UC-Berkeley said identifying the proteins will likely find application in better protecting agricultural crops and horticultural plants against diseases.

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Plant protein 'doorkeepers' block invading microbes, study finds

EUREKALERT
Contact: Patricia Bailey pjbailey@ucdavis.edu, 530-752-9843
University of California - Davis

A group of plant proteins that "shut the door" on bacteria that would otherwise infect the plant's leaves has been identified for the first time by a team of researchers in Denmark, at the
University of California, Davis, and at UC Berkeley.

Findings from the study, which will appear June 29 in the online journal Public Library of Science Biology, provide a better understanding of plants' immune systems and will likely find application in better protecting agricultural crops and horticultural plants against diseases.

"The ability of a plant's immune system to recognize disease-causing microorganisms is critical to the plant's survival and productivity," said Gitta Coaker, a UC Davis plant pathologist and lead author on the study.

"In this study, we identified a complex of proteins in the common research plant Arabidopsis that appear to play important roles in the biochemical mechanisms that enable plants to recognize and block out invading bacteria," Coaker said.

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Plant Microbe Shares Features With Drug-resistant Pathogen

Daniel (Niels) van der Lelie. (Credit: Image courtesy of DOE/Brookhaven National Laboratory)
ScienceDaily (June 16, 2009)

An international team of scientists has discovered extensive similarities between a strain of bacteria commonly associated with plants and one increasingly linked to opportunistic infections in hospital patients. The findings suggest caution in the use of the plant-associated strain for a range of biotech applications.

The genetic analysis was conducted in part at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, and will be published in the July 2009 issue of Nature Reviews Microbiology, now available online.

The research team — which included scientists from Ireland, Austria, and the United Kingdom as well as the U.S. — was investigating the versatility and adaptability of a group of bacteria known as Stenotrophomonas. These bacteria have great metabolic versatility, allowing them to thrive in very diverse environments.

The scientists were particularly interested in comparing two strains of S. maltophilia whose genomes were recently decoded to see why these strains — one isolated as an opportunistic pathogen from a clinical setting (strain K279a), and the other from the roots of poplar trees (strain R551-3) — were so well-suited to their very different environments. Such comparisons are made possible by the high throughput and cost-effective DNA sequencing capacity developed by DOE’s Joint Genome Institute, as well as the Sanger Institute, to help elucidate the role of microorganisms in health, energy, and environmental processes.

“Surprisingly, we observed very few differences between the opportunistic pathogen and the common plant bacterium,” said Brookhaven Lab microbiologist Daniel (Niels) van der Lelie, an expert on soil- and plant-associated microbes, whose team provided the data on the plant-dwelling strain.

For one thing, the scientists found genes that make the bacteria resistant to a wide range of antibiotics in both strains. “This suggests that antibiotic resistance is part of the species’ core genome, and not a trait acquired in the hospital,” van der Lelie said. Multi-drug antibiotic-resistance is one key feature that allows some bacteria to cause deadly infections in hospital patients whose immune systems are often compromised.

The scientists are also intrigued about similarities in the mechanisms the two strains use to colonize their respective environments. For example, both strains possess very similar mechanisms to produce glue-like substances, or biofilms, which allow them to adhere to plant roots, in one case, and medical devices such as ventilation tubes and intravenous catheters, in the other. Such devices are a common source of exposure to opportunistic pathogens for hospital patients.

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