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Parasitism is a type of relationship between two species where one species, the parasite, benefits at the expense of the other, the host. When parasites cause disease in their host they are referred to as pathogens.
Fungal pathogens reorient hyphal growth towards their plant hosts in response to chemical signals; here, directed growth of the plant pathogen Fusarium oxysporum towards the roots of the tomato plant is shown to be triggered by class III peroxidases secreted by the tomato plant, with the fungal response requiring a sex pheromone receptor.
Plants are able to induce defense responses following recognition of certain pathogen derived molecules at the cell surface. Here, Manosalva et al. show that plants respond to ascarosides, a conserved class of nematode pheromones, providing the first example of plant recognition of an animal-derived signalling molecule.
The plant pathogenic fungus Fusarium oxysporum secretes an effector that is similar to a plant peptide hormone, underscoring the variety of mechanisms that plant pathogens have evolved to tamper with host physiology.