Genome Evolution in Plant Pathogens

Pathogen genes that shut down specific host plant immune responses are highly divergent and have evolved rapidly to accommodate adaptation. Food security is of global importance and crop diseases caused by plant pathogens are a major constraint to agriculture worldwide. Many of these pathogens have a similar biotrophic life stage during which they contact host cells and secrete effector proteins that alter plant responses to infection (1). In this issue, comparative genomics studies of closely related pathogen species by Raffaele et al. on page 1540 (2), Baxter et al. on page 1549 (3), Spanu et al. on page 1543 (4), and Schirawski et al. on page 1546 (5) reveal that such effector proteins evolve rapidly and that their diversity contributes to host range and parasite speciation.