American Association for the Advancement of Science, Science, 6170(343), p. 552-555, 2014
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The Makings of a Choosy Pathogen The oomycete Phytophthora infestans is responsible for potato blight. A closely related pathogen afflicts the 4 o'clock flower. To assess why such similar pathogens are restricted to one host or the other, Dong et al. (p. 552 ; see the Perspective by Coaker ) analyzed similar effectors from both pathogens. The results suggest that the host specialization that led to evolutionary divergence depends on reciprocal single–amino acid changes that tailor the pathogen effector to a specific host protease that is being disabled. Thus, small changes can open the door for a pathogen to jump to another species of host and, itself, diversify into another species of pathogen.