title: Microbial priming of plant and animal immunity: symbionts as developmental signals.
abstract: The functional similarity between root and gut microbiota, both contributing to the nutrition and protection of the host, is often overlooked. A central mechanism for efficient protection against pathogens is defense priming, the preconditioning of immunity induced by microbial colonization after germination or birth. Microbiota have been recruited several times in evolution as developmental signals for immunity maturation. Because there is no evidence that microbial signals are more relevant than endogenous ones, we propose a neutral scenario for the evolution of this dependency: any hypothetic endogenous signal can be lost because microbial colonization, reliably occurring at germination or birth, can substitute for it, and without either positive selection or the acquisition of new functions. Dependency of development on symbiotic signals can thus evolve by contingent irreversibility.
authors.affiliation: Muséum National d'Histoire Naturelle, Département Systématique et Evolution, Institut de Systématique, Evolution, Biodiversité (ISYEB, UMR 7205), CP 50, 45 rue Buffon, 75005 Paris, France. Electronic address: ma.selosse@wanadoo.fr.
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Selosse
authors.affiliation: Institut de Biologie de l'Ecole Normale Supérieure, Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 1024, Centre National de la Recherche Scientifique (CNRS) UMR 8197, 75005 Paris, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Bessis
authors.affiliation: Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidin, Consejo Superior de Investigaciones Científicas (CSIC), Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: Pozo
mesh_terms: D000818:Animals; D041981:Gastrointestinal Tract / Q000382:microbiology*; D007109:Immunity; D064307:Microbiota / Q000276:immunology* / Q000502:physiology*; D018517:Plant Roots / Q000382:microbiology*; D013559:Symbiosis
keywords: MAMPs; axeny; gut microbiota; immune system; mycorrhiza; neutral dependency; rhizosphere