Plants employ two modes of their innate immune system to resist pathogen infection. The first mode of immunity is referred to as pattern-triggered immunity (PTI) that is triggered by molecular patterns common to many types of microbes. The second mode is triggered by recognition of pathogen effectors and is called as effector-triggered immunity (ETI). At least some cases of PTI and ETI extensively share downstream signaling machinery, that is, PTI and ETI appear to be mediated by an integrated signaling network. However, activated immune responses in ETI are more prolonged and robust than those in PTI. Furthermore, network analysis has revealed that synergistic relationships among the signaling sectors are evident in PTI, which may amplify the signal, whereas compensatory relationships among the sectors dominate in ETI, explaining the robustness of ETI against genetic and pathogenic perturbations. Thus, plants seem to use a common signaling network differently in PTI and ETI.
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We thank Gerit Bethke and Jane Glazebrook for critical reading of the manuscript. This work was supported by grants IOS-0419648 and MCB-0918908 to F.K. from the National Science Foundation .
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