Plants recognize pathogens through immune-like receptors, which activate a resistance response. In turn, pathogens have evolved means to modify plant signaling pathways to avoid triggering the resistance response. Kay et al. and Römer et al. tackle the molecular mechanisms underlying this evolutionary arms race between plants and pathogens. The bacterial type III effector protein, AvrBs3, functions as a pathogenicity factor in susceptible host plants, which lack a resistance gene known as Bs3, by acting as a transcriptional activator. In contrast, plants carrying Bs3 recognize the AvrBs3 protein and activate the resistance gene Bs3, which simulates the plant resistance pathway.
P. Römer, S. Hahn, T. Jordan, T. Strauß, U. Bonas, T. Lahaye, Plant pathogen recognition mediated by promoter activation of the pepper Bs3 resistance gene. Science 318, 645-648 (2007). [Abstract] [Full Text]