( Researchers have uncovered the link bet...)Study: Plants use dual defense system to fight pathogens

Knowing how these pathways of immunity work may one day help researchers breed plants that can better resist a variety of pathogens, said David Mackey, the study's lead author and an assistant professor of horticulture and crop science at Ohio State University .

He and his colleagues explain their findings in the current issue of the journal Cell.

The researchers infected Arabidopsis plants with a bacterial strain of Pseudomonas syringae, a bacterium that usually infects tomato crops. Both Arabidopsis, a plant of the mustard family, and P. syringae are models that researchers commonly use to conduct basic plant research.

One of the immune pathways that interested the researchers recognizes what they call pathogen-associated molecular patterns, or PAMPs. The PAMP pathway appears to be a plant's first line of defense against pathogenic attackers.

"The PAMP path induces a fairly weak immune response," Mackey said. "Even so, there is growing evidence that suggests these kinds of responses are extremely important in restricting the growth of many pathogens."

The other pathway uses disease-resistant proteins, or R-proteins, which can detect certain molecules, called effectors, that are secreted by pathogens. This pathway produces a stronger immune response than the PAMP pathway, Mackey said.

He and his colleagues found that the R-protein pathway steps in when PAMP is rendered useless by a pathogen.

Certain types of bacteria, including P. syringae, make a hypodermic needle-like structure that pierces the outermost membrane of a healthy plant or animal cell. The pathogen uses this conduit to send infectious effector proteins into the host cell.

While P. syringae injects about 40 different varieties of e
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Source:Ohio State University