DURHAM, N.C. -- Researchers have identified the set of tools an infectious microbe uses to persuade a plant to open the windows and let the bug and all of its friends inside.
The microbe is Pseudomonas syringae, a successful bacterial pathogen that produces characteristic brown spots in more than 50 different species of plant. The signal it uses is a molecule called coronatine, which to the plant looks just like its own jasmonic acid, a signal that is part of the plant's immune system. The pathogen "hijacks" a system that balances the plant's two different defense strategies, said Xinnian Dong, a Duke professor of biology.
Plant pathogens have two basic strategies, Dong said. One approach kills cells and harvests what's left of them for food. The other is more like parasitism, setting up housekeeping in and around living cells and using what they provide. So the plant has two kinds of defenses. Against necrotrophs, the cell-killers, the plant produces jasmonic acid and does what it can to keep cells alive. Faced with biotrophs, the parasitic type, it tries to kill the infected cells. These responses work in opposition to one another and through cross-talk to keep the plant carefully calibrated, depending on the pathogens it encounters.
"Breaking the cross-talk between the systems would be a problem because the plant may respond the wrong way," said Dong, who is also a research fellow of the Howard Hughes Medical Institute (HHMI) and Gordon and Betty Moore Foundation (GBMF). "Pseudomonas is successful by hijacking a critical process in this cross-talk."
"It's all connected," said graduate student Xiao-yu Zheng, who worked on the project for four years. "That's the beauty of it." Zheng is the first author on an article appearing in the June 14 edition of Cell Host & Microbe. The research was supported by the National Science Foundation, the National Institutes of Health and the Department of Energy.
|Contact: Karl Leif Bates|